Marijuana Botany
An Advanced Study:
The Propagation and Breeding of Distinctive Cannabis
by Robert Connell Clarke
Chapter 3 - Genetics and Breeding of Cannabis
The greatest service which can be rendered to
any country is to add a useful plant to its culture.
-Thomas Jefferson
Genetics
Although it is possible to breed Cannabis with limited
success without any knowledge of the laws of inheritance,
the full potential of diligent breeding, and the line of action
most likely to lead to success, is realized by breeders who
have mastered a working knowledge of genetics.
As we know already, all information transmitted from
generation to generation must be contained in the pollen
of the staminate parent and the ovule of the pistillate
parent. Fertilization unites these two sets of genetic infor-
mation, a seed forms, and a new generation is begun. Both
pollen and ovules are known as gametes, and the trans-
mitted units determining the expression of a character are
known as genes. Individual plants have two identical sets of
genes (2n) in every cell except the gametes, which through
reduction division have only one set of genes (in). Upon
fertilization one set from each parent combines to form
a seed (2n).
In Cannabis, the haploid (in) number of chromo-
somes is 10 and the diploid (2n) number of chromosomes
is 20. Each chromosome contains hundreds of genes, influ-
encing every phase of the growth and development of
the plant.
If cross-pollination of two plants with a shared genetic
trait (or self-pollination of a hermaphrodite) results in off-
spring that all exhibit the same trait, and if all subsequent
(inbred) generations also exhibit it, then we say that the
strain (i.e., the line of offspring derived from common an-
cestors) is true-breeding, or breeds true, for that trait. A
strain may breed true for one or more traits while varying
in other characteristics. For example, the traits of sweet
aroma and early maturation may breed true, while off-
spring vary in size and shape. For a strain to breed true for
some trait, both of the gametes forming the offspring must
have an identical complement of the genes that influence
the expression of that trait. For example, in a strain that
breeds true for webbed leaves, any gamete from any parent
in that population will contain the gene for webbed leaves,
which we will signify with the letter w. Since each gamete
carries one-half (in) of the genetic complement of the
offspring, it follows that upon fertilization both "leaf-
shape" genes of the (2n) offspring will be w. That is, the
offspring, like both parents, are ww. In turn, the offspring
also breed true for webbed leaves because they have only
w genes to pass on in their gametes.
On the other hand, when a cross produces offspring
that do not breed true (i.e., the offspring do not all re-
semble their parents) we say the parents have genes that
segregate or are hybrid. Just as a strain can breed true for
one or more traits, it can also segregate for one or more
traits; this is often seen. For example, consider a cross
where some of the offspring have webbed leaves and some
have normal compound-pinnate leaves. (To continue our
system of notation we will refer to the gametes of plants
with compound-pinnate leaves as W for that trait. Since
these two genes both influence leaf shape, we assume that
they are related genes, hence the lower-case w and upper-
case W notation instead of w for webbed and possibly P for
pinnate.) Since the gametes of a true-breeding strain must
each have the same genes for the given trait, it seems logi-
cal that gametes which produce two types of offspring
must have genetically different parents.
Observation of many populations in which offspring
differed in appearance from their parents led Mendel to his
theory of genetics. If like only sometimes produces like,
then what are the rules which govern the outcome of these
crosses? Can we use these rules to predict the outcome of
future crosses?
Assume that we separate two true-breeding popula-
tions of Cannabis, one with webbed and one with
compound-pinnate leaf shapes. We know that all the
gametes produced by the webbed-leaf parents will contain
genes for leaf-shape w and all gametes produced by the
compound-pinnate individuals will have W genes for leaf
shape. (The offspring may differ in other characteristics,
of course.)
If we make a cross with one parent from each of the
true-breeding strains, we will find that 100% of the off-
apring are of the compound-pinnate leaf phenotype. (The
expression of a trait in a plant or strain is known as the
phenotype.) What happened to the genes for webbed leaves
contained in the webbed leaf parent? Since we know that
there were just as many w genes as W genes combined in
the offspring, the W gene must mask the expression of the
w gene. We term the W gene the dominant gene and say
that the trait of compound-pinnate leaves is dominant over
the recessive trait of webbed leaves. This seems logical
since the normal phenotype in Cannabis has compound-
pinnate leaves. It must be remembered, however, that many
useful traits that breed true are recessive. The true-breeding
dominant or recessive condition, WW or ww, is termed the
homozygous condition; the segregating hybrid condition
wW or Ww is called heterozygous. When we cross two of
the F1 (first filial generation) offspring resulting from the
initial cross of the ~1 (parental generation) we observe two
types of offspring. The F2 generation shows a ratio of
approximately 3:1, three compound pinnate type-to-one
webbed type. It should be remembered that phenotype
ratios are theoretical. The real results may vary from the
expected ratios, especially in small samples.
In this case, compound-pinnate leaf is dominant over
webbed leaf, so whenever the genes w and W are combined,
the dominant trait W will be expressed in the phenotype.
In the F2 generation only 25% of the offspring are homo-
zygous for W so only 25% are fixed for W. The w trait is
only expressed in the F2 generation and only when two w
genes are combined to form a double-recessive, fixing the
recessive trait in 25% of the offspring. If compound-pinnate
showed incomplete dominance over webbed, the geno-
types in this example would remain the same, but the
phenotypes in the F1 generation would all be intermediate
types resembling both parents and the F2 phenotype ratio
would be 1 compound-pinnate :2 intermediate :1 webbed.
The explanation for the predictable ratios of offspring
is simple and brings us to Mendel's first law, the first of the
basic rules of heredity:
I. Each of the genes in a related pair segregate from
each other during gamete formation.
A common technique used to deduce the genotype of
the parents is the back-cross. This is done by crossing one
of the F1 progeny back to one of the true-breeding P1
parents. If the resulting ratio of phenotypes is 1:1 (one
heterozygous to one homozygous) it proves that the
parents were indeed homozygous dominant WW and
homozygous-recessive ww.
The 1:1 ratio observed when back-crossing F1 to P1
and the 1:2:1 ratio observed in F1 to F1 crosses are the two
basic Mendelian ratios for the inheritance of one character
controlled by one pair of genes. The astute breeder uses
these ratios to determine the genotype of the parental
plants and the relevance of genotype to further breeding.
This simple example may be extended to include the
inheritance of two or more unrelated pairs of genes at a
time. For instance we might consider the simultaneous
inheritance of the gene pairs T (tall)/t (short) and M (early
maturation)/m (late maturation). This is termed a poly-
hybrid instead of monohybrid cross. Mendel's second law
allows us to predict the outcome of polyhybrid crosses
also:
II. Unrelated pairs of genes are inherited indepen-
dently of each other.
If complete dominance is assumed for both pairs of
genes, then the 16 possible F2 genotype combinations will
form 4 F2 phenotypes in a 9:3:3:1 ratio, the most frequent
of which is the double-dominant tall/early condition. In-
complete dominance for both gene pairs would result in 9
F2 phenotypes in a 1:2:1:2:4:2:1:2:1 ratio, directly re-
flecting the genotype ratio. A mixed dominance condition
would result in 6 F2 phenotypes in a 6:3:3:2:1:1 ratio.
Thus, we see that a cross involving two independently
assorting pairs of genes results in a 9:3:3:1 Mendelian
phenotype ratio only if dominance is complete. This ratio
may differ, depending on the dominance conditions present
in the original gene pairs. Also, two new phenotypes,
tall/late and short/early, have been created in the F2 genera-
tion; these phenotypes differ from both parents and grand-
parents. This phenomenon is termed recombination and
explains the frequent observation that like begets like, but
not exactly like.
A polyhybrid back-cross with two unrelated gene
pairs exhibits a 1:1 ratio of phenotypes as in the mono-
hybrid back-cross. It should be noted that despite domi-
nance influence, an F1 back-cross with the P1 homozygous-
recessive yields the homozygous-recessive phenotype
short/late 25% of the time, and by the same logic, a back-
cross with the homozygous-dominant parent will yield the
homozygous dominant phenotype tall/early 25% of the
time. Again, the back-cross proves invaluable in determin-
ing the F1 and P1 genotypes. Since all four phenotypes of
the back-cross progeny contain at least one each of both
recessive genes or one each of both dominant genes, the
back-cross phenotype is a direct representation of the four
possible gametes produced by the F1 hybrid.
So far we have discussed inheritance of traits con-
trolled by discrete pairs of unrelated genes. Gene inter-
action is the control of a trait by two or more gene pairs.
In this case genotype ratios will remain the same but
phenotype ratios may be altered. Consider a hypothetical
example where 2 dominant gene pairs Pp and Cc control
late-season anthocyanin pigmentation (purple color) in
Cannabis. If P is present alone, only the leaves of the plant
(under the proper environmental stimulus) will exhibit
accumulated anthocyanin pigment and turn a purple color.
If C is present alone, the plant will remain green through-
out its life cycle despite environmental conditions. If both
are present, however, the calyxes of the plant will also ex-
hibit accumulated anthocyanin and turn purple as the
leaves do. Let us assume for now that this may be a desir-
able trait in Cannabis flowers. What breeding techniques
can be used to produce this trait?
First, two homozygous true-breeding ~1 types are
crossed and the phenotype ratio of the F1 offspring is
observed.
The phenotypes of the F2 progeny show a slightly
altered phenotype ratio of 9:3:4 instead of the expected
9:3:3:1 for independently assorting traits. If P and C must
both be present for any anthocyanin pigmentation in leaves
or calyxes, then an even more distorted phenotype ratio of
9:7 will appear.
Two gene pairs may interact in varying ways to pro-
duce varying phenotype ratios. Suddenly, the simple laws
of inheritance have become more complex, but the data
may still be interpreted.
Summary of Essential Points of Breeding
1 - The genotypes of plants are controlled by genes
which are passed on unchanged from generation to
generation.
2 - Genes occur in pairs, one from the gamete of the
staminate parent and one from the gamete of the pistillate
parent.
3 - When the members of a gene pair differ in their
effect upon phenotype, the plant is termed hybrid or
heterozygous.
4 - When the members of a pair of genes are equal in
their effect upon phenotype, then they are termed true-
breeding or homozygous.
5 - Pairs of genes controlling different phenotypic
traits are (usually) inherited independently.
6 - Dominance relations and gene interaction can
alter the phenotypic ratios of the F1, F2, and subsequent
generations.
Polyploidy
Polyploidy is the condition of multiple sets of chro-
mosomes within one cell. Cannabis has 20 chromosomes in
the vegetative diploid (2n) condition. Triploid (3n) and
tetraploid (4n) individuals have three or four sets of chro-
mosomes and are termed polyploids. It is believed that the
haploid condition of 10 chromosomes was likely derived
by reduction from a higher (polyploid) ancestral number
(Lewis, W. H. 1980). Polyploidy has not been shown to
occur naturally in Cannabis; however, it may be induced
artificially with colchicine treatments. Colchicine is a poi-
sonous compound extracted from the roots of certain
Colchicum species; it inhibits chromosome segregation to
daughter cells and cell wall formation, resulting in larger
than average daughter cells with multiple chromosome
sets. The studies of H. E. Warmke et al. (1942-1944) seem
to indicate that colchicine raised drug levels in Cannabis. It
is unfortunate that Warmke was unaware of the actual
psychoactive ingredients of Cannabis and was therefore
unable to extract THC. His crude acetone extract and
archaic techniques of bioassay using killifish and small
freshwater crustaceans are far from conclusive. He was,
however, able to produce both triploid and tetraploid
strains of Cannabis with up to twice the potency of dip-
bid strains (in their ability to kill small aquatic organisms).
The aim of his research was to "produce a strain of hemp
with materially reduced marijuana content" and his results
indicated that polyploidy raised the potency of Cannabis
without any apparent increase in fiber quality or yield.
Warmke's work with polyploids shed light on the
nature of sexual determination in Cannabis. He also illus-
trated that potency is genetically determined by creating a
lower potency strain of hemp through selective breeding
with low potency parents.
More recent research by A. I. Zhatov (1979) with
fiber Cannabis showed that some economically valuable
traits such as fiber quantity may be improved through
polyploidy. Polyploids require more water and are usually
more sensitive to changes in environment. Vegetative
growth cycles are extended by up to 30-40% in polyploids.
An extended vegetative period could delay the flowering of
polyploid drug strains and interfere with the formation of
floral clusters. It would be difficult to determine if canna-
binoid levels had been raised by polyploidy if polyploid
plants were not able to mature fully in the favorable part
of the season when cannabinoid production is promoted
by plentiful light and warm temperatures. Greenhouses
and artificial lighting can be used to extend the season and
test polyploid strains.
The height of tetraploid (4n) Cannabis in these exper-
iments often exceeded the height of the original diploid
plants by 25-30%. Tetraploids were intensely colored,
with dark green leaves and stems and a well developed
gross phenotype. Increased height and vigorous growth, as
a rule, vanish in subsequent generations. Tetraploid plants
often revert back to the diploid condition, making it diffi-
cult to support tetraploid populations. Frequent tests are
performed to determine if ploidy is changing.
Triploid (3n) strains were formed with great difficulty
by crossing artificially created tetraploids (4n) with dip-
bids (2n). Triploids proved to be inferior to both diploids
and tetraploids in many cases.
De Pasquale et al. (1979) conducted experiments with
Cannabis which was treated with 0.25% and 0.50% solu-
tions of colchicine at the primary meristem seven days
after generation. Treated plants were slightly taller and
possessed slightly larger leaves than the controls, Anoma-
lies in leaf growth occurred in 20% and 39%, respectively,
of the surviving treated plants. In the first group (0.25%)
cannabinoid levels were highest in the plants without
anomalies, and in the second group (0.50%) cannabinoid
levels were highest in plants with anomalies, Overall,
treated plants showed a 166-250% increase in THC with
respect to controls and a decrease of CBD (30-33%) and
CBN (39-65%). CBD (cannabidiol) and CBN (cannabinol)
are cannabinoids involved in the biosynthesis and degrada-
tion of THC. THC levels in the control plants were very
low (less than 1%). Possibly colchicine or the resulting
polyploidy interferes with cannabinoid biogenesis to favor
THC. In treated plants with deformed leaf lamina, 90% of
the cells are tetraploid (4n 40) and 10% diploid (2n 20).
In treated plants without deformed lamina a few cells are
tetraploid and the remainder are triploid or diploid.
The transformation of diploid plants to the tetraploid
level inevitably results in the formation of a few plants
with an unbalanced set of chromosomes (2n + 1, 2n - 1,
etc.). These plants are called aneuploids. Aneuploids are
inferior to polyploids in every economic respect. Aneu-
ploid Cannabis is characterized by extremely small seeds.
The weight of 1,000 seeds ranges from 7 to 9 grams (1/4
to 1/3 ounce). Under natural conditions diploid plants do
not have such small seeds and average 14-19 grams (1/2-
2/3 ounce) per 1,000 (Zhatov 1979).
Once again, little emphasis has been placed on the
relationship between flower or resin production and poly-
ploidy. Further research to determine the effect of poly-
ploidy on these and other economically valuable traits of
Cannabis is needed.
Colchicine is sold by laboratory supply houses, and
breeders have used it to induce polyploldy in Cannabis.
However, colchicine is poisonous, so special care is exer-
cised by the breeder in any use of it. Many clandestine
cultivators have started polyploid strains with colchicine.
Except for changes in leaf shape and phyllotaxy, no out-
standing characteristics have developed in these strains and
potency seems unaffected. However, none of the strains
have been examined to determine if they are actually poly
ploid or if they were merely treated with colchicine to no
effect. Seed treatment is the most effective and safest way
to apply colchicine. * In this way, the entire plant growing
from a colchicine-treated seed could be polyploid and if
any colchicine exists at the end of the growing season the
amount would be infinitesimal. Colchicine is nearly always
lethal to Cannabis seeds, and in the treatment there is a
very fine line between polyploidy and death. In other
words, if 100 viable seeds are treated with colchicine and
40 of them germinate it is unlikely that the treatment in-
duced polyploidy in any of the survivors. On the other
hand, if 1,000 viable treated seeds give rise to 3 seedlings,
the chances are better that they are polyploid since the
treatment killed all of the seeds but those three. It is still
necessary to determine if the offspring are actually poly-
ploid by microscopic examination.
The work of Menzel (1964) presents us with a crude
map of the chromosomes of Cannabis, Chromosomes 2-6
and 9 are distinguished by the length of each arm. Chromo-
some 1 is distinguished by a large knob on one end and a
dark chromomere 1 micron from the knob. Chromosome 7
is extremely short and dense, and chromosome 8 is assumed
to be the sex chromosome. In the future, chromosome
*The word "safest" is used here as a relative term. Coichicine has
received recent media attention as a dangerous poison and while
these accounts are probably a bit too lurid, the real dangers of expo-
iure to coichicine have not been fully researched. The possibility of
bodily harm exists and this is multiplied when breeders inexperi-
enced in handling toxins use colchicine. Seed treatment might be
safer than spraying a grown plant but the safest method of all is to
not use colchicine.
mapping will enable us to picture the location of the genes
influencing the phenotype of Cannabis. This will enable
geneticists to determine and manipulate the important
characteristics contained in the gene pool. For each trait
the number of genes in control will be known, which
chromosomes carry them, and where they are located
along those chromosomes.
Breeding
All of the Cannabis grown in North America today
originated in foreign lands. The diligence of our ancestors
in their collection and sowing of seeds from superior
plants, together with the forces of natural selection, have
worked to create native strains with localized characteris-
tics of resistance to pests, diseases, and weather conditions.
In other words, they are adapted to particular niches in the
ecosystem. This genetic diversity is nature's way of pro-
tecting a species. There is hardly a plant more flexible than
Cannabis. As climate, diseases, and pests change, the strain
evolves and selects new defenses, programmed into the ge-
netic orders contained in each generation of seeds. Through
the importation in recent times of fiber and drug Cannabis,
a vast pool of genetic material has appeared in North Amer-
ica. Original fiber strains have escaped and become acclima-
tized (adapted to the environment), while domestic drug
strains (from imported seeds) have, unfortunately, hybrid-
ized and acclimatized randomly, until many of the fine
gene combinations of imported Cannabis have been lost.
Changes in agricultural techniques brought on by
technological pressure, greed, and full-scale eradication
programs have altered the selective pressures influencing
Cannabis genetics. Large shipments of inferior Cannabis
containing poorly selected seeds are appearing in North
America and elsewhere, the result of attempts by growers
and smugglers to supply an ever increasing market for mari-
juana. Older varieties of Cannabis, associated with long-
standing cultural patterns, may contain genes not found in
the newer commercial varieties. As these older varieties and
their corresponding cultures become extinct, this genetic
information could be lost forever. The increasing popular-
ity of Cannabis and the requirements of agricultural tech-
nology will call for uniform hybrid races that are likely to
displace primitive populations worldwide.
Limitation of genetic diversity is certain to result
from concerted inbreeding for uniformity. Should inbred
Cannabis be attacked by some previously unknown pest or
disease, this genetic uniformity could prove disastrous due
to potentially resistant diverse genotypes having been
dropped from the population. If this genetic complement
of resistance cannot be reclaimed from primitive parental
material, resistance cannot be introduced into the ravaged
population. There may also be currently unrecognized
favorable traits which could be irretrievably dropped from
the Cannabis gene pool. Human intervention can create
new phenotypes by selecting and recombining existing
genetic variety, but only nature can create variety in the
gene pool itself, through the slow process of random
mutation.
This does not mean that importation of seed and
selective hybridization are always detrimental. Indeed
these principles are often the key to crop improvement,
but only when applied knowledgeably and cautiously. The
rapid search for improvements must not jeopardize the
pool of original genetic information on which adaptation
relies. At this time, the future of Cannabis lies in govern-
ment and clandestine collections. These collections are
often inadequate, poorly selected and badly maintained.
Indeed, the United Nations Cannabis collection used as the
primary seed stock for worldwide governmental research
is depleted and spoiled.
Several steps must be taken to preserve our vanishing
genetic resources, and action must be immediate:
• Seeds and pollen should be collected directly from
reliable and knowledgeable sources. Government seizures
and smuggled shipments are seldom reliable seed sources.
The characteristics of both parents must be known; conse-
quently, mixed bales of randomly pollinated marijuana are
not suitable seed sources, even if the exact origin of the
sample is certain. Direct contact should be made with the
farmer-breeder responsible for carrying on the breeding
traditions that have produced the sample. Accurate records
of every possible parameter of growth must be kept with
carefully stored triplicate sets of seeds.
• Since Cannabis seeds do not remain viable forever,
even under the best storage conditions, seed samples should
he replenished every third year. Collections should be
planted in conditions as similar as possible to their original
niche and allowed to reproduce freely to minimize natural
and artificial selection of genes and ensure the preservation
of the entire gene pool. Half of the original seed collection
should be retained until the viability of further generations
is confirmed, and to provide parental material for compari-
son and back-crossing. Phenotypic data about these subse-
quent generations should be carefully recorded to aid in
understanding the genotypes contained in the collection.
Favorable traits of each strain should be characterized and
catalogued.
• It is possible that in the future, Cannabis cultiva-
tion for resale, or even personal use, may be legal but only
for approved, patented strains. Special caution would be
needed to preserve variety in the gene pool should the
patenting of Cannabis strains become a reality.
• Favorable traits must be carefully integrated into
existing strains.
The task outlined above is not an easy one, given the
current legal restrictions on the collection of Cannabis
seed. In spite of this, the conscientious cultivator is making
a contribution toward preserving and improving the genet-
ics of this interesting plant.
Even if a grower has no desire to attempt crop im-
provement, successful strains have to be protected so they
do not degenerate and can be reproduced if lost. Left to
the selective pressures of an introduced environment, most
drug strains will degenerate and lose potency as they accli-
matize to the new conditions. Let me cite an example of a
typical grower with good intentions.
A grower in northern latitudes selected an ideal spot
to grow a crop and prepared the soil well. Seeds were
selected from the best floral clusters of several strains avail-
able over the past few years, both imported and domestic.
Nearly all of the staminate plants were removed as they
matured and a nearly seedless crop of beautiful plants re-
sulted. After careful consideration, the few seeds from
accidental pollination of the best flowers were kept for the
following season, These seeds produced even bigger and
better plants than the year before and seed collection was
performed as before. The third season, most of the plants
were not as large or desirable as the second season, but
there were many good individuals. Seed collection and cul-
tivation the fourth season resulted in plants inferior even to
the first crop, and this trend continued year after year.
What went wrong? The grower collected seed from the best
plants each year and grew them under the same conditions.
The crop improved the first year. Why did the strain
degenerate?
This example illustrates the unconscious selection for
undesirable traits. The hypothetical cultivator began well
by selecting the best seeds available and growing them
properly. The seeds selected for the second season resulted
from random hybrid pollinations by early-flowering or
overlooked staminate plants and by hermaphrodite pistil-
late plants. Many of these random pollen-parents may be
undesirable for breeding since they may pass on tendencies
toward premature maturation, retarded maturation, or
hermaphrodism. However, the collected hybrid seeds pro-
duce, on the average, larger and more desirable offspring
than the first season. This condition is called hybrid vigor
and results from the hybrid crossing of two diverse gene
pools. The tendency is for many of the dominant charac-
teristics from both parents to be transmitted to the F1 off-
spring, resulting in particularly large and vigorous plants.
This increased vigor due to recombination of dominant
genes often raises the cannabinoid level of the F1 offspring,
but hybridization also opens up the possibility that unde-
sirable (usually recessive) genes may form pairs and express
their characteristics in the F2 offspring. Hybrid vigor may
also mask inferior qualities due to abnormally rapid growth.
During the second season, random pollinations again
accounted for a few seeds and these were collected. This
selection draws on a huge gene pool and the possible F2
combinations are tremendous. By the third season the gene
pool is tending toward early-maturing plants that are accli-
matized to their new conditions instead of the drug-
producing conditions of their native environment. These
acclimatized members of the third crop have a higher
chance of maturing viable seeds than the parental types,
and random pollinations will again increase the numbers of
acclimatized individuals, and thereby increase the chance
that undesirable characteristics associated with acclimati-
zation will be transmitted to the next F2 generation. This
effect is compounded from generation to generation and
finally results in a fully acclimatized weed strain of little
drug value.
With some care the breeder can avoid these hidden
dangers of unconscious selection. Definite goals are vital to
progress in breeding Cannabis. What qualities are desired in
a strain that it does not already exhibit? What character-
istics does a strain exhibit that are unfavorable and should
be bred out? Answers to these questions suggest goals for
breeding. In addition to a basic knowledge of Cannabis
botany, propagation, and genetics, the successful breeder
also becomes aware of the most minute differences and
similarities in phenotype. A sensitive rapport is established
between breeder and plants and at the same time strict
guidelines are followed. A simplified explanation of the
time-tested principles of plant breeding shows how this
works in practice.
Selection is the first and most important step in the
breeding of any plant. The work of the great breeder and
plant wizard Luther Burbank stands as a beacon to breeders
of exotic strains. His success in improving hundreds of
flower, fruit, and vegetable crops was the result of his
meticulous selection of parents from hundreds of thou-
sands of seedlings and adults from the world over.
Bear in mind that in the production of any new
plant, selection plays the all-important part.
First, one must get clearly in mind the kind of
plant he wants, then breed and select to that end,
always choosing through a series of years the
plants which are approaching nearest the ideal,
and rejecting all others.
-Luther Burbank (in James, 1964)
Proper selection of prospective parents is only possible
if the breeder is familiar with the variable characteristics of
Cannabis that may be genetically controlled, has a way to
accurately measure these variations, and has established
goals for improving these characteristics by selective breed-
ing. A detailed list of variable traits of Cannabis, including
parameters of variation for each trait and comments per-
taining to selective breeding for or against it, are found at
the end of this chapter. By selecting against unfavorable
traits while selecting for favorable ones, the unconscious
breeding of poor strains is avoided.
The most important part of Burbank's message on
selection tells breeders to choose the plants "which are ap-
proaching nearest the ideal," and REJECT ALL OTHERS!
Random pollinations do not allow the control needed to
reject the undesirable parents. Any staminate plant that
survives detection and roguing (removal from the popula-
tion), or any stray staminate branch on a pistillate her-
maphrodite may become a pollen parent for the next gen-
eration. Pollination must be controlled so that only the
pollen- and seed-parents that have been carefully selected
for favorable traits will give rise to the next generation.
Selection is greatly improved if one has a large sample
to choose from! The best plant picked from a group of 10
has far less chance of being significantly different from its
fellow seedlings than the best plant selected from a sample
of 100,000. Burbank often made his initial selections of
parents from samples of up to 500,000 seedlings. Difficul-
ties arise for many breeders because they lack the space to
keep enough examples of each strain to allow a significant
selection. A Cannabis breeder's goals are restricted by the
amount of space available. Formulating a well defined goal
lowers the number of individuals needed to perform effec-
tive crosses. Another technique used by breeders since the
time of Burbank is to make early selections. Seedling
plants take up much less space than adults. Thousands of
seeds can be germinated in a flat. A flat takes up the same
space as a hundred 10-centimeter (4-inch) sprouts or six-
teen 30-centimeter (12-inch) seedlings or one 60-centimeter
(24-inch) juvenile. An adult plant can easily take up as
much space as a hundred flats. Simple arithmetic shows
that as many as 10,000 sprouts can be screened in the
space required by each mature plant, provided enough seeds
are available. Seeds of rare strains are quite valuable and
exotic; however, careful selection applied to thousands of
individuals, even of such common strains as those from
Colombia or Mexico, may produce better offspring than
plants from a rare strain where there is little or no oppor-
tunity for selection after germination. This does not mean
that rare strains are not valuable, but careful selection is
even more important to successful breeding. The random
pollinations that produce the seeds in most imported mari-
juana assure a hybrid condition which results in great seed-
ling diversity. Distinctive plants are not hard to discover if
the seedling sample is large enough.
Traits considered desirable when breeding Cannabis
often involve the yield and quality of the final product, but
these characteristics can only be accurately measured after
the plant has been harvested and long after it is possible to
select or breed it. Early seedling selection, therefore, only
works for the most basic traits. These are selected first, and
later selections focus on the most desirable characteristics
exhibited by juvenile or adult plants. Early traits often give
clues to mature phenotypic expression, and criteria for
effective early seedling selection are easy to establish. As an
example, particularly tall and thin seedlings might prove to
be good parents for pulp or fiber production, while seed-
lings of short internode length and compound branching
may be more suitable for flower production. However,
many important traits to be selected for in Cannabis floral
clusters cannot be judged until long after the parents are
gone, so many crosses are made early and selection of seeds
made at a later date.
Hybridization is the process of mixing differing gene
pools to produce offspring of great genetic variation from
which distinctive individuals can be selected. The wind
performs random hybridization in nature. Under cultiva-
tion, breeders take over to produce specific, controlled
hybrids. This process is also known as cross-pollination,
cross-fertilization, or simply crossing. If seeds result, they
will produce hybrid offspring exhibiting some characteris-
tics from each parent.
Large amounts of hybrid seed are most easily pro-
duced by planting two strains side by side, removing the
staininate plants of the seed strain, and allowing nature to
take its course. Pollen- or seed-sterile strains could be devel
oped for the production of large amounts of hybrid seed
without the labor of thinning; however, genes for sterility
are rare. It is important to remember that parental weak-
nesses are transmitted to offspring as well as strengths.
Because of this, the most vigorous, healthy plants are al-
ways used for hybrid crosses.
Also, sports (plants or parts of plants carrying and
expressing spontaneous mutations) most easily transmit
mutant genes to the offspring if they are used as pollen
parents. If the parents represent diverse gene pools, hybrid
vigor results, because dominant genes tend to carry valu-
able traits and the differing dominant genes inherited from
each parent mask recessive traits inherited from the other.
This gives rise to particularly large, healthy individuals. To
increase hybrid vigor in offspring, parents of different geo-
graphic origins are selected since they will probably repre-
sent more diverse gene pools.
Occasionally hybrid offspring will prove inferior to
both parents, but the first generation may still contain
recessive genes for a favorable characteristic seen in a par-
ent if the parent was homozygous for that trait. First gen-
eration (F1) hybrids are therefore inbred to allow recessive
genes to recombine and express the desired parental trait.
Many breeders stop with the first cross and never realize
the genetic potential of their strain. They fail to produce
an F2 generation by crossing or self-pollinating F1 offspring.
Since most domestic Cannabis strains are F1 hybrids for
many characteristics, great diversity and recessive recombi-
nation can result from inbreeding domestic hybrid strains.
In this way the breeding of the F1 hybrids has afready been
accomplished, and a year is saved by going directly to F2
hybrids. These F2 hybrids are more likely to express reces-
sive parental traits. From the F2 hybrid generation selec-
tions can be made for parents which are used to start new
true-breeding strains. Indeed, F2 hybrids might appear with
more extreme characteristics than either of the P~ parents.
(For example, P1 high-THC X P1 low-THC yields F1 hybrids
of intermediate THC content. Selfing the F1 yields F2 hy-
brids, of both P1 [high and low THC] phenotypes, inter-
mediate F1 phenotypes, and extra-high THC as well as
extra-low THC phenotypes.)
Also, as a result of gene recombination, F1 hybrids
are not true-breeding and must be reproduced from the
original parental strains. When breeders create hybrids they
try to produce enough seeds to last for several successive
years of cultivation, After initial field tests, undesirable
hybrid seeds are destroyed and desirable hybrid seeds
stored for later use. If hybrids are to be reproduced, a clone
is saved from each parental plant to preserve original paren-
tal genes.
Back-crossing is another technique used to produce
offspring with reinforced parental characteristics. In this
case, a cross is made between one of the F~ or subsequent
offspring and either of the parents expressing the desired
trait. Once again this provides a chance for recombination
and possible expression of the selected parental trait. Back-
crossing is a valuable way of producing new strains, but it is
often difficult because Cannabis is an annual, so special
care is taken to save parental stock for back-crossing the
following year. Indoor lighting or greenhouses can be used
to protect breeding stock from winter weather. In tropical
areas plants may live outside all year. In addition to saving
particular parents, a successful breeder always saves many
seeds from the original P1 group that produced the valuable
characteristic so that other P1 plants also exhibiting the
characteristic can be grown and selected for back-crossing
at a later time.
Several types of breeding are summarized as follows:
1 - Crossing two varieties having outstanding qualities
(hybridization).
2 - Crossing individuals from the F1 generation or
selfing F1 individuals to realize the possibilities of the ori-
ginal cross (differentiation).
3 - Back crossing to establish original parental types.
4 - Crossing two similar true-breeding (homozygous)
varieties to preserve a mutual trait and restore vigor.
It should be noted that a hybrid plant is not usually
hybrid for all characteristics nor does a true-breeding strain
breed true for all characteristics. When discussing crosses,
we are talking about the inheritance of one or a few traits
only. The strain may be true-breeding for only a few traits,
hybrid for the rest. Monohybrid crosses involve one trait,
dihybrid crosses involve two traits, and so forth. Plants
have certain limits of growth, and breeding can only pro-
duce a plant that is an expression of some gene already
present in the total gene pool. Nothing is actually created
by breeding; it is merely the recombination of existing
genes into new genotypes. But the possibilities of recombi-
nation are nearly limitless.
The most common use of hybridization is to cross two
outstanding varieties. Hybrids can be produced by crossing
selected individuals from different high-potency strains of
different origins, such as Thailand and Mexico. These two
parents may share only the characteristic of high psycho-
activity and differ in nearly every other respect. From this
great exchange of genes many phenotypes may appear in
the F2 generation. From these offspring the breeder selects
individuals that express the best characteristics of the par-
ents. As an example, consider some of the offspring from
the P1 (parental) cross: Mexico X Thailand. In this case,
genes for high drug content are selected from both parents
while other desirable characteristics can be selected from
either one. Genes for large stature and early maturation
are selected from the Mexican seed-parent, and genes for
large calyx size and sweet floral aroma are selected from
the Thai pollen parent. Many of the F1 offspring exhibit
several of the desired characteristics. To further promote
gene segregation, the plants most nearly approaching the
ideal are crossed among themselves. The F2 generation is a
great source of variation and recessive expression. In the F2
generation there are several individuals out of many that
exhibit all five of the selected characteristics. Now the
process of inbreeding begins, using the desirable F2 parents.
If possible, two or more separate lines are started,
never allowing them to interbreed. In this case one accept-
able staminate plant is selected along with two pistillate
plants (or vice versa). Crosses between the pollen parent
and the two seed parents result in two lines of inheritance
with slightly differing genetics, but each expressing the
desired characteristics. Each generation will produce new,
more acceptable combinations.
If two inbred strains are crossed, F1 hybrids will be
less variable than if two hybrid strains are crossed. This
comes from limiting the diversity of the gene pools in the
two strains to be hybridized through previous inbreeding.
Further independent selection and inbreeding of the best
plants for several generations will establish two strains
which are true-breeding for all the originally selected traits.
This means that all the offspring from any parents in the
strain will give rise to seedlings which all exhibit the
selected traits. Successive inbreeding may by this time have
resulted in steady decline in the vigor of the strain.
When lack of vigor interferes with selecting pheno-
types for size and hardiness, the two separately selected
strains can then be interbred to recombine nonselected
genes and restore vigor. This will probably not interfere
with breeding for the selected traits unless two different
gene systems control the same trait in the two separate
lines, and this is highly unlikely. Now the breeder has pro-
duced a hybrid strain that breeds true for large size, early
maturation, large sweet-smelling calyxes, and high THC
level. The goal has been reached!
Wind pollination and dioecious sexuality favor a heter-
ozygous gene pool in Cannabis. Through Anbreeding, hy-
brids are adapted from a heterozygous gene pool to a
homozygous gene pool, providing the genetic stability
needed to create true-breeding strains. Establishing pure
strains enables the breeder to make hybrid crosses with a
better chance of predicting the outcome. Hybrids can be
created that are not reproducible in the F2 generation.
Commercial strains of seeds could be developed that
would have to be purchased each year, because the F1
hybrids of two pure-bred lines do not breed true. Thus, a
seed breeder can protect the investment in the results of
breeding, since it would be nearly impossible to reproduce
the parents from F2 seeds.
At this time it seems unlikely that a plant patent
would be awarded for a pure-breeding strain of drug Can-
nabis. In the future, however, with the legalization of cul-
tivation, it is a certainty that corporations with the time,
space, and money to produce pure and hybrid strains of
Cannabis will apply for patents. It may be legal to grow
only certain patented strains produced by large seed com-
panies. Will this be how government and industry combine
to control the quality and quantity of "drug" Cannabis?
Acclimatization
Much of the breeding effort of North American culti-
vators is concerned with acclimatizing high-THC strains of
equatorial origin to the climate of their growing area while
preserving potency. Late-maturing, slow, and irregularly
flowering strains like those of Thailand have difficulty
maturing in many parts of North America. Even ~:n a green-
house, it may not be possible to mature plants to their full
native potential.
To develop an early-maturing and rapidly flowering
8train, a breeder may hybridize as in the previous example.
However, if it is important to preserve unique imported
genetics, hybridizing may be inadvisable. Alternatively, a
pure cross is made between two or more Thai plants that
most closely approach the ideal in blooming early. At this
point the breeder may ignore many other traits and aim at
breeding an earlier-maturing variety of a pure Thai strain.
This strain may still mature considerably later than is ideal
for the particular location unless selective pressure is ex-
erted. If further crosses are made with several individuals
that satisfy other criteria such as high THC content, these
may be used to develop another pure Thai strain of high
THC content. After these true-breeding lines have been
established, a dihybrid pure cross can be made in an
attempt to produce an F1 generation containing early-
maturing, high-THC strains of pure Thai genetics, in other
words, an acclimatized drug strain.
Crosses made without a clear goal in mind lead to
strains that acclimatize while losing many favorable charac-
teristics. A successful breeder is careful not to overlook a
characteristic that may prove useful. It is imperative that
original imported Cannabis genetics be preserved intact to
protect the species from loss of genetic variety through ex-
cessive hybridization. A currently unrecognized gene may
be responsible for controlling resistance to a pest or disease,
and it may only be possible to breed for this gene by back-
crossing existing strains to original parental gene pools.
Once pure breeding lines have been established, plant
breeders classify and statistically analyze the offspring to
determine the patterns of inheritance for that trait. This is
the system used by Gregor Mendel to formulate the basic
laws of inheritance and aid the modern breeder in predict-
ing the outcome of crosses,
1 - Two pure lines of Cannabis that differ in a particu-
lar trait are located.
2 - These two pure-breeding lines are crossed to pro-
duce an F1 generation.
3 - The F1 generation is inbred.
4 - The offspring of the F1 and F2 generations are
classified with regard to the trait being studied.
5 - The results are analyzed statistically.
6 - The results are compared to known patterns of
inheritance so the nature of the genes being selected for
can be characterized.
Fixing Traits
Fixing traits (producing homozygous offspring) in
Cannabis strains is more difficult than it is in many other
flowering plants. With monoecious strains or hermaphro-
dites it is possible to fix traits by self-pollinating an individ-
ual exhibiting favorable traits. In this case one plant acts as
both mother and father. However, most strains of Cannabis
are dioecious, and unless hermaphroditic reactions can be
induced, another parent exhibiting the trait is required to
fix the trait. If this is not possible, the unique individual
may be crossed with a plant not exhibiting the trait, inbred
in the F1 generation, and selections of parents exhibiting
the favorable trait made from the F2 generation, but this is
very difficult.
If a trait is needed for development of a dioecious
strain it might first be discovered in a monoecious strain
and then fixed through selfing and selecting homozygous
offspring. Dioecious individuals can then be selected from
the monoecious population and these individuals crossed
to breed out monoecism in subsequent generations.
Galoch (197
indicated that gibberellic acid (GA3)
promoted stamen production while indoleacetic acid (IAA),
ethrel, and kinetin promoted pistil production in prefloral
dioecious Cannabis. Sex alteration has several useful appli-
cations. Most importantly, if only one parent expressing a
desirable trait can be found, it is difficult to perform a
cross unless it happens to be a hermaphrodite plant. Hor-
mones might be used to change the sex of a cutting from
the desirable plant, and this cutting used to mate with it.
This is most easily accomplished by changing a pistillate
cutting to a staminate (pollen) parent, using a spray of 100
ppm gibberellic acid in water each day for five consecutive
days. Within two weeks staminate flowers may appear.
Pollen can then be collected for selfing with the original
pistillate parent. Offspring from the cross should also be
mostly pistillate since the breeder is selfing for pistillate
sexuality. Staminate parents reversed to pistillate floral
production make inferior seed-parents since few pistillate
flowers and seeds are formed.
If entire crops could be manipulated early in life to
produce all pistillate or staminate plants, seed production
and seedless drug Cannabis production would be greatly
facilitated.
Sex reversal for breeding can also be accomplished by
mutilation and by photoperiod alteration. A well-rooted,
flourishing cutting from the parent plant is pruned back
to 25% of its original size and stripped of all its remaining
flowers. New growth will appear within a few days, and
several flowers of reversed sexual type often appear.
Flowers of the unwanted sex are removed until the cutting
is needed for fertilization. Extremely short light cycles
(6-8 hour photoperiod) can also cause sex reversal. How-
ever, this process takes longer and is much more difficult
to perform in the field.
Genotype and Phenotype Ratios
It must be remembered, in attempting to fix favorable
characteristics, that a monohybrid cross gives rise to four
possible recombinant genotypes, a dihybrid cross gives rise
to 16 possible recombinant genotypes, and so forth.
Phenotype and genotype ratios are probabilistic. If
recessive genes are desired for three traits it is not effective
to raise only 64 offspring and count on getting one homo-
zygous recessive individual. To increase the probability of
success it is better to raise hundreds of offspring, choosing
only the best homozygous recessive individuals as future
parents. All laws of inheritance are based on chance and
offspring may not approach predicted ratios until many
more have been phenotypically characterized and grouped
than the theoretical minimums.
The genotype of each individual is expressed by a
mosaic of thousands of subtle overlapping traits. It is the
sum total of these traits that determines the general pheno-
type of an individual. It is often difficult to determine if
the characteristic being selected is one trait or the blending
of several traits and whether these traits are controlled by
one or several pairs of genes. It often makes little difference
that a breeder does not have plants that are proven to breed
true. Breeding goals can still be established. The selfing of
F1 hybrids will often give rise to the variation needed in
the F2 generation for selecting parents for subsequent gen-
erations, even if the characteristics of the original parents
of the F1 hybrid are not known. It is in the following gen-
erations that fixed characteristics appear and the breeding
of pure strains can begin. By selecting and crossing individ-
uals that most nearly approach the ideal described by the
breeding goals, the variety can be continuously improved
even if the exact patterns of inheritance are never deter-
mined. Complementary traits are eventually combined into
one line whose seeds reproduce the favorable parental
traits. Inbreeding strains also allows weak recessive traits to
express themselves and these abnormalities must be dili-
gently removed from the breeding population. After five or
six generations, strains become amazingly uniform. Vigor is
occasionally restored by crossing with other lines or by
backcrossing.
Parental plants are selected which most nearly ap-
proach the ideal. If a desirable trait is not expressed by the
parent, it is much less likely to appear in the offspring. It is
imperative that desirable characteristics be hereditary and
not primarily the result of environment and cultivation.
Acquired traits are not hereditary and cannot be made
hereditary. Breeding for as few traits as possible at one
time greatly increases the chance of success. In addition to
the specific traits chosen as the aims of breeding, parents
are selected which possess other generally desirable traits
such as vigor and size. Determinations of dominance and
recessiveness can only be made by observing the outcome
of many crosses, although wild traits often tend to be
dominant. This is one of the keys to adaptive survival.
However, all the possible combinations will appear in the
F2 generation if it is large enough, regardless of dominance.
Now, after further simplifying this wonderful system
of inheritance, there are additional exceptions to the rules
which must be explored. In some cases, a pair of genes
may control a trait but a second or third pair of genes is
needed to express this trait. This is known as gene inter-
action. No particular genetic attribute in which we may be
interested is totally isolated from other genes and the ef-
fects of environment. Genes are occasionally transferred
in groups instead of assorting independently. This is known
as gene linkage, These genes are spaced along the same
chromosome and may or may not control the same trait.
The result of linkage might be that one trait cannot be in-
herited without another. At times, traits are associated with
the X and Y sex chromosomes and they may be limited to
expression in only one sex (sex linkage). Crossing over also
interferes with the analysis of crosses. Crossing over is the
exchanging of entire pieces of genetic material between two
chromosomes. This can result in two genes that are nor-
mally linked appearing on separate chromosomes where
they will be independently inherited. All of these processes
can cause crosses to deviate from the expected Mendelian
outcome. Chance is a major factor in breeding Cannabis, or
any introduced plant, and the more crosses a breeder
attempts the higher are the chances of success.
Variate, isolate, intermate, evaluate, multiplicate, and
disseminate are the key words in plant improvement. A
plant breeder begins by producing or collecting various
prospective parents from which the most desirable ones
are selected and isolated. Intermating of the select parents
results in offspring which must be evaluated for favorable
characteristics. If evaluation indicates that the offspring are
not improved, then the process is repeated. Improved off-
spring are multiplied and disseminated for commercial use.
Further evaluation in the field is necessary to check for
uniformity and to choose parents for further intermating.
This cyclic approach provides a balanced system of plant
improvement.
The basic nature of Cannabis makes it challenging to
breed. Wind pollination and dioecious sexuality, which
account for the great adaptability in Cannabis, cause many
problems in breeding, but none of these are insurmount-
able. Developing a knowledge and feel for the plant is more
important than memorizing Mendelian ratios. The words of
the great Luther Burbank say it well, "Heredity is indelibly
fixed by repetition."
The first set of traits concerns Cannabis plants as
a whole while the remainder concern the qualities of
seedlings, leaves, fibers, and flowers. Finally a list of
various Cannabis strains is provided along with specific
characteristics. Following this order, basic and then specific
selections of favorable characteristics can be made.
List of Favorable Traits of Cannabis
in Which Variation Occurs
1. General Traits
a) Size and Yield
b) Vigor
c) Adaptability
d) Hardiness
e) Disease and Pest Resistance
f) Maturation
g) Root Production
h) Branching
i) Sex
2. Seedling Traits
3. Leaf Traits
4. Fiber Traits
5. Floral Traits
a) Shape
b) Form
c) Calyx Size
d) Color
e) Cannabinoid Level
f) Taste and Aroma
g) Persistence of Aromatic Principles
and Cannabinoids
h) Trichome Type
i) Resin Quantity and Quality
j) Resin Tenacity
k) Drying and Curing Rate
I) Ease of Manicuring
m) Seed Characteristics
n) Maturation
o) Flowering
p) Ripening
q) Cannabinoid Profile
6. Gross Phenotypes of Cannabis Strains
1. General Traits
a) Size and Yield - The size of an individual Cannabis plant
is determined by environmental factors such as room for
root and shoot growth, adequate light and nutrients, and
proper irrigation. These environmental factors influence
the phenotypic image of genotype, but the genotype of the
individual is responsible for overall variations in gross mor-
phology, including size. Grown under the same conditions,
particularly large and small individuals are easily spotted
and selected. Many dwarf Cannabis plants have been re-
ported and dwarfism may be subject to genetic control, as
it is in many higher plants, such as dwarf corn and citrus.
Cannabis parents selected for large size tend to produce
offspring of a larger average size each year. Hybrid crosses
between tall (Cannabis sativa-Mexico) strains and short
(Cannabis ruderalis-Russia) strains yield F1 offspring of
intermediate height (Beutler and der Marderosian 197
.
Hybrid vigor, however, will influence the size of offspring
more than any other genetic factor. The increased size of
hybrid offspring is often amazing and accounts for much of
the success of Cannabis cultivators in raising large plants.
It is not known whether there is a set of genes for "gigan-
tism" in Cannabis or whether polyploid individuals really
yield more than diploid due to increased chromosome
count. Tetraploids tend to be taller and their water re-
quirements are often higher than diploids. Yield is deter-
mined by the overall production of fiber, seed, or resin and
selective breeding can be used to increase the yield of any
one of these products. However, several of these traits may
be closely related, and it may be impossible to breed for
one without the other (gene linkage). Inbreeding of a pure
strain increases yield only if high yield parents are selected.
High yield plants, staminate or pistillate, are not finally
selected until the plants are dried and manicured. Because
of this, many of the most vigorous plants are crossed and
seeds selected after harvest when the yield can be measured.
b) Vigor - Large size is often also a sign of healthy vig-
orous growth. A plant that begins to grow immediately
will usually reach a larger size and produce a higher yield
in a short growing season than a sluggish, slow-growing
plant. Parents are always selected for rich green foliage and
rapid, responsive growth. This will ensure that genes for
certain weaknesses in overall growth and development are
bred out of the population while genes for strength and
vigor remain.
c) Adaptability - It is important for a plant with a wide
distribution such as Cannabis to be adaptable to many
different environmental conditions. Indeed, Cannabis is
one of the most genotypically diverse and phenotypically
plastic plants on earth; as a result it has adapted to environ-
mental conditions ranging from equatorial to temperate
climates. Domestic agricultural circumstances also dictate
that Cannabis must be grown under a great variety of
conditions,
Plants to be selected for adaptability are cloned and
grown in several locations. The parental stocks with the
highest survival percentages can be selected as prospective
parents for an adaptable strain. Adaptability is really just
another term for hardiness under varying growth conditions.
d) Hardiness - The hardiness of a plant is its overall resis-
tance to heat and frost, drought and overwatering, and so
on. Plants with a particular resistance appear when adverse
conditions lead to the death of the rest of a large popula-
tion. The surviving few members of the population might
carry inheritable resistance to the environmental factor
that destroyed the majority of the population. Breeding
these survivors, subjecting the offspring to continuing stress
conditions, and selecting carefully for several generations
should result in a pure-breeding strain with increased resis-
tance to drought, frost, or excessive heat.
e) Disease and Pest Resistance - In much the same way as
for hardiness a strain may be bred for resistance to a certain
disease, such as damping-off fungus. If flats of seedlings are
infected by damping-off disease and nearly all of them die,
the remaining few will have some resistance to damping-off
fungus. If this resistance is inheritable, it can be passed on
to subsequent generations by crossing these surviving
plants. Subsequent crossing, tested by inoculating flats of
seedling offspring with damping-off fungus, should yield a
more resistant strain.
Resistance to pest attack works in much the same
way. It is common to find stands of Cannabis where one or
a few plants are infested with insects while adjacent plants
are untouched. Cannabinoid and terpenoid resins are most
probably responsible for repelling insect attack, and levels
of these vary from plant to plant. Cannabis has evolved
defenses against insect attack in the form of resin-secreting
glandular trichomes, which cover the reproductive and
associated vegetative structures of mature plants. Insects,
finding the resin disagreeable, rarely attack mature Canna-
bis flowers. However, they may strip the outer leaves of the
same plant because these develop fewer glandular tri-
chomes and protective resins than the flowers. Nonglandu-
lar cannabinoids and other compounds produced within
leaf and stem tissues which possibly inhibit insect attack,
may account for the varying resistance of seedlings and
vegetative juvenile plants to pest infestation. With the pop-
ularity of greenhouse Cannabis cultivation, a strain is
needed with increased resistance to mold, mite, aphid,- or
white fly infestation. These problems are often so severe
that greenhouse cultivators destroy any plants which are
attacked. Molds usually reproduce by wind-borne spores,
so negligence can rapidly lead to epidemic disaster. Selec-
tion and breeding of the least infected plants should result
in strains with increased resistance.
f) Maturation - Control of the maturation of Cannabis is
very important no matter what the reason for growing it.
If Cannabis is to be grown for fiber it is important that the
maximum fiber content of the crop be reached early and
that all of the individuals in the crop mature at the same
time to facilitate commercial harvesting. Seed production
requires the even maturation of both pollen and seed par-
ents to ensure even setting and maturation of seeds. An
uneven maturation of seeds would mean that some seeds
would drop and be lost while others are still ripening. An
understanding of floral maturation is the key to the pro-
duction of high quality drug Cannabis. Changes in gross
morphology are accompanied by changes in cannabinoid
and terpenoid production and serve as visual keys to deter-
mining the ripeness of Cannabis flowers.
A Cannabis plant may mature either early or late,
be fast or slow to flower, and ripen either evenly or
sequentially.
Breeding for early or late maturation is certainly a
reality; it is also possible to breed for fast or slow flowering
and even or sequential ripening. In general, crosses between
early-maturing plants give rise to early-maturing offspring,
crosses between late-maturing plants give rise to late-
maturing offspring, and crosses between late- and early-
maturing plants give rise to offspring of intermediate
maturation. This seems to indicate that maturation of
Cannabis is not controlled by the simple dominance and
recessiveness of one gene but probably results from incom-
plete dominance and a combination of genes for separate
aspects of maturation. For instance, Sorghum maturation
is controlled by four separate genes. The sum of these
genes produces a certain phenotype for maturation. Al-
though breeders do not know the action of each specific
gene, they still can breed for the total of these traits and
achieve results more nearly approaching the goal of timely
maturation than the parental strains.
g) Root Production - The size and shape of Cannabis root
systems vary greatly. Although every embryo sends out a
taproot from which lateral roots grow, the individual
growth pattern and final size and shape of the roots vary
considerably. Some plants send out a deep taproot, up to
1 meter (39 inches) long, which helps support the plant
against winds and rain. Most Cannabis plants, however,
produce a poor taproot which rarely extends more than
30 centimeters (1 foot). Lateral growth is responsible for
most of the roots in Cannabis plants. These fine lateral
roots offer the plant additional support but their primary
function is to absorb water and nutrients from the soil. A
large root system will be able to feed and support a large
plant. Most lateral roots grow near the surface of the soil
where there is more water, more oxygen, and more avail-
able nutrients. Breeding for root size and shape may prove
beneficial for the production of large rain- and wind-
resistant strains. Often Cannabis plants, even very large
ones, have very small and sensitive root systems. Recently,
certain alkaloids have been discovered in the roots of Can-
nab is that might have some medical value. If this proves
the case, Cannabis may be cultivated and bred for high
alkaloid levels in the roots to be used in the commercial
production of pharmaceuticals.
As with many traits, it is difficult to make selections
for root types until the parents are harvested. Because of
this many crosses are made early and seeds selected later.
h) Branching - The branching pattern of a Cannabis plant
is determined by the frequency of nodes along each branch
and the extent of branching at each node. For examples,
consider a tall, thin plant with slender limbs made up of
long internodes and nodes with little branching (Oaxaca,
Mexico strain). Compare this with a stout, densely branched
plant with limbs of short internodes and highly branched
nodes (Hindu Kush hashish strains). Different branching
patterns are preferred for the different agricultural applica-
tions of fiber, flower, or resin production. Tall, thin plants
with long internodes and no branching are best adapted to
fiber production; a short, broad plant with short inter-
nodes and well developed branching is best adapted to
floral production. Branching structure is selected that will
tolerate heavy rains and high winds without breaking. This
is quite advantageous to outdoor growers in temperate
zones with short seasons. Some breeders select tall, limber
plants (Mexico) which bend in the wind; others select
short, stiff plants (Hindu Kush) which resist the weight of
water without bending.
i) Sex - Attempts to breed offspring of only one sexual
type have led to more misunderstanding than any other
facet of Cannabis genetics. The discoveries of McPhee
(1925) and Schaffner (192
showed that pure sexual type
and hermaphrodite conditions are inherited and that the
percentage of sexual types could be altered by crossing
with certain hermaphrodites. Since then it has generally
been assumed by researchers and breeders that a cross be-
tween ANY unselected hermaphrodite plant and a pistillate
seed-parent should result in a population of all pistillate
offspring. This is not the case. In most cases, the offspring
of hermaphrodite parents tend toward hermaphrodism,
which is largely unfavorable for the production of Cannabis
other than fiber hemp. This is not to say that there is no
tendency for hermaphrodite crosses to alter sex ratios in
the offspring. The accidental release of some pollen fro
predominantly pistillate hermaphrodites, along with the
complete eradication of nearly every staminate and stami-
nate hermaphrodite plant may have led to a shift in sexual
ratio in domestic populations of sinsemilla drug Cannabis.
It is commonly observed that these strains tend toward
60% to 80% pistillate plants and a few pistillate hermaph-
rodites are not uncommon in these populations.
However, a cross can be made which will produce
nearly all pistillate or staminate individuals. If the proper
pistillate hermaphrodite plant is selected as the pollen-
parent and a pure pistillate plant is selected as the seed-
parent it is possible to produce an F1, and subsequent
generations, of nearly all pistillate offspring. The proper
pistillate hermaphrodite pollen-parent is one which has
grown as a pure pistillate plant and at the end of the sea-
son, or under artificial environmental stress, begins to
develop a very few staminate flowers. If pollen from these
few staminate flowers forming on a pistillate plant is applied
to a pure pistillate seed parent, the resulting F1 generation
should be almost all pistillate with only a few pistillate
hermaphrodites. This will also be the case if the selected
pistillate hermaphrodite pollen source is selfed and bears
its own seeds. Remember that a selfed hermaphrodite
gives rise to more hermaphrodites, but a selfed pistillate
plant that has given rise to a limited number of staminate
flowers in response to environmental stresses should give
rise to nearly all pistillate offspring. The F1 offspring may
have a slight tendency to produce a few staminate flowers
under further environmental stress and these are used to
produce F2 seed. A monoecious strain produces 95+%
plants with many pistillate and staminate flowers, but a
dioecious strain produces 95+% pure pistillate or staminate
plants. A plant from a dioecious strain with a few inter-
sexual flowers is a pistillate or staminate hermaphrodite.
Therefore, the difference between monoecism and her-
maphrodism is one of degree, determined by genetics and
environment.
Crosses may also be performed to produce nearly all
staminate offspring. This is accomplished by crossing a
pure staminate plant with a staminate plant that has pro-
duced a few pistillate flowers due to environmental stress,
or selfing the latter plant. It is readily apparent that in the
wild this is not a likely possibility. Very few staminate
plants live long enough to produce pistillate flowers, and
when this does happen the number of seeds produced is
limited to the few pistillate flowers that occur. In the case
of a pistillate hermaphrodite, it may produce only a few
staminate flowers, but each of these may produce thou-
sands of pollen grains, any one of which may fertilize one
of the plentiful pistillate flowers, producing a seed. This is
another reason that natural Cannabis populations tend
toward predominantly pistillate and pistillate hermaphro-
dite plants. Artificial hermaphrodites can be produced by
hormone sprays, mutilation, and altered light cycles. These
should prove most useful for fixing traits and sexual type.
Drug strains are selected for strong dioecious tenden-
cies. Some breeders select strains with a sex ratio more
nearly approaching one than a strain with a high pistillate
sex ratio. They believe this reduces the chances of pistillate
plants turning hermaphrodite later in the season.
2. Seedling Traits
Seedling traits can be very useful in the efficient and
purposeful selection of future parental stock. If accurate
selection can be exercised on small seedlings, much larger
populations can be grown for initial selection, as less space
is required to raise small seedlings than mature plants.
Whorled phyllotaxy and resistance to damping-off are two
traits that may be selected just after emergence of the em-
bryo from the soil. Early selection for vigor, hardiness,
resistance, and general growth form may be made when
the seedlings are from 30 to 90 centimeters (1 to 3 feet)
tall. Leaf type, height, and branching are other criteria for
early selection. These early-selected plants cannot be bred
until they mature, but selection is the primary and most
important step in plant improvement.
Whorled phyllotaxy is associated with subsequent
anomalies in the growth cycle (i.e., multiple leaflets and
flattened or clubbed stems). Also, most whorled plants are
staminate and whorled phyllotaxy may be sex-linked.
3. Leaf Traits
Leaf traits vary greatly from strain to strain. In addi-
tion to these regularly occurring variations in leaves, there
are a number of mutations and possible traits in leaf shape.
It may turn out that leaf shape is correlated with other
traits in Cannabis. Broad leaflets might be associated with
a low calyx-to-leaf ratio and narrow leaflets might be asso-
ciated with a high calyx-to-leaf ratio. If this is the case,
early selection of seedlings by leaflet shape could determine
the character of the flowering clusters at harvest. Both
compound and webbed leaf variations seem to be heredi-
tary, as are general leaf characteristics. A breeder may wish
to develop a unique leaf shape for an ornamental strain or
increase leaf yield for pulp production.
A peculiar leaf mutation was reported from an F1-
Colombian plant in which two leaves on the plant, at the
time of flowering, developed floral clusters of 5-10 pistil-
late calyxes at the intersection of the leaflet array and the
petiole attachment, on the adaxial (top) side of the leaf.
One of these clusters developed a partial staminate flower
but fertilization was unsuccessful. It is unknown if this
mutation is hereditary.
From Afghanistan, another example has been observed
with several small floral clusters along the petioles of many
of the large primary leaves.
4. Fiber Traits
More advanced breeding has occurred in fiber strains
than any other type of Cannabis. Over the years many
strains have been developed with improved maturation, in-
creased fiber content, and improved fiber quality as re-
gards length, strength, and suppleness. Extensive breeding
programs have been carried on in France, Italy, Russia, and
the United States to develop better varieties of fiber Can-
nabis. Tall limbless strains that are monoecious are most
desirable. Monoeciousness is favored, because in dioecious
populations the staminate plants will mature first and the
fibers will become brittle before the pistillate plants are
ready for harvest. The fiber strains of Europe are divided
into northern and southern varieties. The latter require
higher temperatures and a longer vegetative period and as a
result grow taller and yield more fiber.
5. Floral Traits
Many individual traits determine the floral character-
istics of Cannabis This section will focus on the individual
traits of pistillate floral clusters with occasional comments
about similar traits in staminate floral clusters. Pistillate
flowering clusters are the seed-producing organs of Canna-
bis; they remain on the plant and go through many changes
that cannot be compared to staminate plants.
a) Shape - The basic shape of a floral cluster is determined
by the internode lengths along the main floral axis and
within individual floral clusters. Dense, long clusters result
when internodes are short along a long floral axis and there
are short internodes within the individual compact floral
clusters (Hindu Kush). Airy clusters result when a plant
forms a stretched floral axis with long internodes between
well-branched individual floral clusters (Thailand).
The shape of a floral cluster is also determined by the
general growth habit of the plant. Among domestic Canna-
bis phenotypes, for instance, it is obvious that floral clus-
ters from a creeper phenotype plant will curve upwards at
the end, and floral clusters from the huge upright pheno-
type will have long, straight floral clusters of various shapes.
Early in the winter, many strains begin to stretch and cease
calyx production in preparation for rejuvenation and sub-
sequent vegetative growth in the spring. Staminate plants
also exhibit variation in floral clusters. Some plants have
tight clusters of staminate calyxes resembling inverted
grapes (Hindu Kush) and others have long, hanging groups
of flowers on long, exposed, leafless branches (Thailand).
b) Form - The form of a floral cluster is determined by
the numbers and relative proportions of calyxes and
flowers. A leafy floral cluster might be 70% leaves and
have a calyx-to-leaf ratio of 1-to-4. It is obvious that
strains with a high calyx-to-leaf ratio are more adapted to
calyx production, and therefore, to resin production. This
factor could be advantageous in characterizing plants as fu-
ture parents of drug strains. At this point it must be noted
that pistillate floral clusters are made up of a number of
distinct parts. They include stems, occasional seeds, calyxes,
inner leaves subtending calyx pairs (small, resinous, 1-3
leaflets), and outer leaves subtending entire floral clusters
(larger, little resin, 3-11 leaflets). The ratios (by dry weight)
of these various portions vary by strain, degree of pollina-
tion, and maturity of the floral clusters. Maturation is a
reaction to environmental change, and the degree of matur-
ity reached is subject to climatic limits as well as breeder's
preference. Because of this interplay between environment
and genetics in the control of floral form it is often difficult
to breed Cannabis for floral characteristics. A thorough
knowledge of the way a strain matures is important in
separating possible inherited traits of floral clusters from
acquired traits. Chapter IV, Maturation and Harvesting of
Cannabis, delves into the secrets and theories of matura-
tion. For now, we will assume that the following traits are
described from fully mature floral clusters (peak floral
stage) before any decline.
c) Calyx Size - Mature calyxes range in size from 2 to 12
millimeters (1/16 to 3/8 inch) in length. Calyx size is
largely dependent upon age and maturity. Calyx size of a
floral cluster is best expressed as the average length of the
mature viable calyxes. Calyxes are still considered viable if
both pistils appear fresh and have not begun to curl or
change colors. At this time, the calyx is relatively straight
and has not begun to swell with resin and change shape as
it will when the pistils die. It is generally agreed that the
production of large calyxes is often as important in deter-
mining the psychoactivity of a strain as the quantity of
calyxes produced. Hindu Kush, Thai, and Mexican strains
are some of the most psychoactive strains, and they are
often characterized by large calyxes and seeds.
Calyx size appears to be an inherited trait in Cannabis.
Completely acclimatized hybrid strains usually have many
rather small calyxes, while imported strains with large
calyxes retain that size when inbred.
Initial selection of large seeds increases the chance
that offspring will be of the large-calyx variety. Aberrant
calyx development occasionally results in double or fused
calyxes, both of which may set seed. This phenomenon is
most pronounced in strains from Thailand and India.
d) Color - The perception and interpretation of color in
Cannabis floral clusters is heavily influenced by the imagi-
nation of the cultivator or breeder. A gold strain does not
appear metallic any more than a red strain resembles a fire
engine. Cannabis floral clusters are basically green, but
changes may take place later in the season which alter the
color to include various shades. The intense green of chloro-
phyll usually masks the color of accessory pigments, Chlo-
rophyll tends to break down late in the season and antho-
cyanin pigments also contained in the tissues are unmasked
and allowed to show through. Purple, resulting from antho-
cyanin accumulation, is the most common color in living
Cannabis, other than green. This color modification is usu-
ally triggered by seasonal change, much as the leaves of
many deciduous trees change color in the fall. This does
not mean, however, that expression of color is controlled
by environment alone and is not an inheritable trait. For
purple color to develop upon maturation, a strain must
have the genetically controlled metabolic potential to pro-
duce anthocyanin pigments coupled with a responsiveness
to environmental change such that anthocyanin pigments
are unmasked and become visible. This also means that a
strain could have the genes for expression of purple color
but the color might never be expressed if the environmental
conditions did not trigger anthocyanin pigmentation or
chlorophyll breakdown. Colombian and Hindu Kush strains
often develop purple coloration year after year when sub-
jected to low night temperatures during maturation. Color
changes will be discussed in more detail in Chapter IV-
Maturation and Harvesting of Cannabis.
Carotenoid pigments are largely responsible for the
yellow, orange, red, and brown colors of Cannabis. They
also begin to show in the leaves and calyxes of certain
strains as the masking green chlorophyll color fades upon
maturation. Gold strains are those which tend to reveal
underlying yellow and orange pigments as they mature.
Red strains are usually closer to reddish brown in color,
although certain carotenoid and anthocyanin pigments are
nearly red and localized streaks of these colors occasionally
appear in the petioles of very old floral clusters. Red color
in pressed, imported tops is often a result of masses of
reddish brown dried pistils.
Several different portions of floral cluster anatomy
may change colors, and it is possible that different genes
may control the coloring of these various parts.
The petioles, adaxial (top) surfaces, and abaxial (bot-
tom) surfaces of leaves, as well as the stems, calyxes, and
pistils color differently in various strains. Since most of the
outer leaves are removed during manicuring, the color ex-
pressed by the calyxes and inner leaves during the late
flowering stages will be all that remains in the final prod-
uct. This is why strains are only considered to be truly
purple or gold if the calyxes maintain those colors when
dried. Anthocyanin accumulation in the stems is sometimes
considered a sign of phosphorus deficiency but in most
situations results from unharmful excesses of phosphorus
or it is a genetic trait. Also, cold temperatures might inter-
fere with phosphorus uptake resulting in a deficiency. Pis-
tils in Hindu Kush strains are quite often magenta or pink
in color when they first appear. They are viable at this
time and turn reddish brown when they wither, as in most
strains. Purple coloration usually indicates that pistillate
plants are over-mature and cannabinoid biosynthesis is
slowing down during cold autumn weather.
e) Cannabinoid Level - Breeding Cannabis for cannabinoid
level has been accomplished by both licensed legitimate
and clandestine researchers. Warmke (1942) and Warmke
and Davidson (1943-44) showed that they could signifi-
cantly raise or lower the cannabinoid level by selective
breeding. Small (1975a) has divided genus Cannabis into
four distinct chemotypes based on the relative amounts of
THC and CBD. Recent research has shown that crosses be-
tween high THC: low CBD strains and low THC: high CBD
strains yield offspring of cannabinoid content intermediate
between the two parents. Beutler and der Marderosian
(197
analyzed the F1 offspring of the controlled cross
C. Sativa (Mexico-high THC) X C. ruderalis (Russia-low
THC) and found that they fell into two groups intermedi-
ate between the parents in THC level. This indicates that
THC production is most likely controlled by more than
one gene. Also the F1 hybrids of lower THC (resembling
the staminate parent) were twice as frequent as the higher
THC hybrids (resembling the pistillate parent). More re-
search is needed to learn if THC production in Cannabis is
associated with the sexual type of the high THC parent or
if high THC characteristics are recessive. According to
Small (1979) the cannabinoid ratios of strains grown in
northern climates are a reflection of the cannabinoid ratio
of the pure, imported, parental strain. This indicates that
cannabinoid phenotype is genetically controlled, and the
levels of the total cannabinoids are determined by environ-
ment. Complex highs produced by various strains of drug
Cannabis may be blended by careful breeding to produce
hybrids of varying psychoactivity, but the level of total
psychoactivity is dependent on environment. This is also
the telltale indication that unconscious breeding with un-
desirable low-THC parents could rapidly lead to the degen-
eration rather than improvement of a drug strain. It is ob-
vious that individuals of fiber strains are of little if any
use in breeding drug strains.
Breeding for cannabinoid content and the eventual
characterization of varying highs produced by Cannabis is
totally subjective guesswork without the aid of modern
analysis techniques. A chromatographic analysis system
would allow the selection of specific cannabinoid types,
especially staminate pollen parents. Selection of staminate
parents always presents a problem when breeding for can-
nabinoid content. Staminate plants usually express the
same ratios of cannabinoids as their pistiliate counterparts
but in much lower quantities, and they are rarely allowed
to reach full maturity for fear of seeding the pistillate por-
tion of the crop. A simple bioassay for THC content of
staminate plants is performed by leaving a series of from
three to five numbered bags of leaves and tops of various
prospective pollen parents along with some rolling papers
in several locations frequented by a steady repeating crowd
of marijuana smokers. The bag completely consumed first
can be considered the most desirable to smoke and possibly
the most psychoactive. It would be impossible for one per-
son to objectively select the most psychoactive staminate
plant since variation in the cannabinoid profile is subtle.
The bioassay reported here is in effect an unstructured
panel evaluation which averages the opinions of unbiased
testers who are exposed to only a few choices at a time.
Such bioassay results can enter into selecting the staminate
parent.
It is difficult to say how many genes might control
THC-acid synthesis. Genetic control of the biosynthetic
pathway could occur at many points through the action of
enzymes controlling each individual reaction. It is generally
accepted that drug strains have an enzyme system which
quickly converts CBD-acid to THC-acid, favoring THC-acid
accumulation. Fiber strains lack this enzyme activity, so
CBD-acid accumulalion is favored since there is little con-
version to THC-acid. These same enzyme systems are
probably also sensitive to changes in heat and light.
It is supposed that variations in the type of high asso-
ciated with different strains of Cannabis result from vary-
ing levels of cannabinoids. THC is the primary psycho-
active ingredient which is acted upon synergistically by
small amounts of CBN, CBD, and other accessory cannabi-
noids. Terpenes and other aromatic constituents of Canna-
bis might also potentiate or suppress the effect of THC. We
know that cannabinoid levels may be used to establish
cannabinoid phenotypes and that these phenotypes are
passed on from parent to offspring. Therefore, cannabi-
noid levels are in part determined by genes. To accurately
characterize highs from various individuals and establish
criteria for breeding strains with particular cannabinoid
contents, an accurate and easy method is needed for meas-
uring cannabinoid levels in prospective parents. Inheritance
and expression of cannabinoid chemotype is certainly
complex.
f) Taste and Aroma - Taste and aroma are closely linked.
As our senses for differentiating taste and aroma are con-
nected, so are the sources of taste and aroma in Cannabis.
Aroma is produced primarily by aromatic terpenes pro-
duced as components of the resin secreted by glandular
trichomes on the surface of the calyxes and subtending
leaflets. When a floral cluster is squeezed, the resinous
heads of glandular trichomes rupture and the aromatic ter-
penes are exposed to the air. There is often a large differ-
ence between the aroma of fresh and dry floral clusters.
This is explained by the polymerization (joining together in
a chain) of many of the smaller molecules of aromatic ter-
penes to form different aromatic and nonaromatic terpene
polymers. This happens as Cannabis resins age and mature,
both while the plant is growing and while curing after har-
vest. Additional aromas may interfere with the primary
terpenoid components, such as ammonia gas and other
gaseous products given off by the curing, fermentation or
spoilage of the tissue (non-resin) portion of the floral
clusters.
A combination of at least twenty aromatic terpenes
(103 are known to occur in Cannabis) and other aromatic
compounds control the aroma of each plant. The produc-
tion of each aromatic compound may be influenced by
many genes; therefore, it is a complex matter to breed
Cannabis for aroma. Breeders of perfume roses often are
amazed at the complexity of the genetic control of aroma,
Each strain, however, has several characteristic aromas, and
these are occasionally transmitted to hybrid offspring such
that they resemble one or both parents in aroma. Many
times breeders complain that their strain has lost the de-
sired aromatic characteristics of the parental strains. Fixed
hybrid strains will develop a characteristic aroma that is
hereditary and often true-breeding. The cultivator with
preservation of a particular aroma as a goal can clone the
individual with a desired aroma in addition to breeding it.
This is good insurance in case the aroma is lost in the off-
spring by segregation and recombination of genes.
The aromas of fresh or dried clusters are sampled and
compared in such a way that they are separated to avoid
confusion. Each sample is placed in the corner of a twice-
folded, labeled piece of unscented writing paper at room
temperature (above 650). A light squeeze will release the
aromatic principles contained within the resin exuded by
the ruptured glandular trichome head. When sampling,
never squeeze a floral cluster directly, as the resins will ad-
here to the fingers and bias further sampling. The folded
paper conveniently holds the floral cluster, avoids confu-
sion during sampling, and contains the aromas as a glass
does in wine tasting.
Taste is easily sampled by loosely rolling dried floral
clusters in a cigarette paper and inhaling to draw a taste
across the tongue. Samples should be approximately the
same size.
Taste in Cannabis is divided into three categories
according to usage: the taste of the aromatic components
carried by air that passes over the Cannabis when it is in-
haled without being lighted; the taste of the smoke from
burning Cannabis; and the taste of Cannabis when it is con-
sumed orally. These three are separate entities.
The terpenes contained in a taste of unlighted Canna-
bis are the same as those sensed in the aroma, but perceived
through the sense of taste instead of smell. Orally ingested
Cannabis generally tastes bitter due to the vegetative plant
tissues, but the resin is characteristically spicy and hot,
somewhat like cinnamon or pepper. The taste of Cannabis
smoke is determined by the burning tissues and vaporizing
terpenes. These terpenes may not be detected in the aroma
and unlighted taste.
Biosynthetic relationships between terpenes and can-
nabinoids have been firmly established. Indeed, cannabi-
noids are synthesized within the plant from terpene
precursors. It is suspected that changes in aromatic ter-
pene levels parallel changes in cannabinoid levels during
maturation. As connections between aroma and psycho-
activity are uncovered, the breeder will be better able to
make field selections of prospective high-THC parents
without complicated analysis.
g) Persistence of Aromatic Principles and Cannabinoids -
Cannabis resins deteriorate as they age, and the aromatic
principles and cannabinoids break down slowly until they
are hardly noticeable. Since fresh Cannabis is only available
once a year in temperate regions, an important breeding
goal has been a strain that keeps well when packaged.
Packageability and shelf life are important considerations
in the breeding of fresh fruit species and will prove equally
important if trade in Cannabis develops after legalization.
h) Trichome Type - Several types of trichomes are present
on the epidermal surfaces of Cannabis. Several of these
trichomes are glandular and secretory in nature and are
divided into bulbous, capitate sessile, and capitate stalked
types. Of these, the capitate stalked glandular trichomes
are apparently responsible for the intense secretion of
cannabinoid laden resins. Plants with a high density of
capitate stalked trichomes are a logical goal for breeders of
drug Cannabis. The number and type of trichomes is
easily characterized by observation with a small hand lens
(lOX to 50X). Recent research by V. P. Soroka (1979)
concludes that a positive correlation exists between the
number of glandular trichomes on leaves and calyxes and
the various cannabinoid contents of the floral clusters. In
other words, many capitate stalked trichomes means higher
THC levels.
i) Resin Quantity and Quality - Resin production by the
glandular trichomes varies. A strain may have many glandu-
lar trichomes but they may not secrete very much resin.
Resin color also varies from strain to strain. Resin heads
may darken and become more opaque as they mature, as
suggested by several authors. Some strains, however, pro-
duce fresh resins that are transparent amber instead of clear
and colorless, and these are often some of the most psycho-
active strains. Transparent resins, regardless of color, are a
sign that the plant is actively carrying out resin biosynthe-
sis. When biosynthesis ceases, resins turn opaque as canna-
binoid and aromatic levels decline. Resin color is certainly
an indication of the conditions inside the resin head, and
this may prove to be another important criterion for
breeding.
j) Resin Tenacity - For years strains have been bred for
hashish production. Hashish is formed from detached resin
heads. In modern times it might be feasible to breed a
strain with high resin production that gives up its precious
covering of resin heads with only moderate shaking, rather
than the customary flailing that also breaks up the plant.
This would facilitate hashish production. Strains that are
bred for use as marijuana would benefit from extremely
tenacious resin heads that would not fall off during packag-
ing and shipment.
k) Drying and Curing Rate - The rate and extent to
which Cannabis dries is generally determined by the way it
is dried, but, all conditions being the same, some strains
dry much more rapidly and completely than others. It is
assumed that resin has a role in preventing desiccation and
high resin content might retard drying. However, it is a
misconception that resin is secreted to coat and seal the
surface of the calyxes and leaves. Resin is secreted by glan-
dular trichomes, but they are trapped under a cuticle layer
surrounding the head cells of the trichome holding the
resin away from the surface of the leaves. There it would
rarely if ever have a chance to seal the surface of the epi-
dermal layer and prevent the transpiration of water. It
seems that an alternate reason must be found for the great
variations in rate and extent of drying. Strains may be bred
that dry and cure rapidly to save valuable time.
1) Ease of Manicuring - One of the most time-consuming
aspects of commercial drug Cannabis production is the
seemingly endless chore of manicuring, or removing the
larger leaves from the floral clusters. These larger outer
leaves are not nearly as psychoactive as the inner leaves
and calyxes, so they are usually removed before selling as
marijuana. Strains with fewer leaves obviously require less
time to manicure. Long petioles on the leaves facilitate
removal by hand with a small pair of scissors. If there is a
marked size difference between very large outer leaves and
tiny, resinous inner leaves it is easier to manicure quickly
because it is easier to see which leaves to remove.
m) Seed Characteristics - Seeds may be bred for many
characteristics including size, oil content, and protein con-
tent. Cannabis seed is a valuable source of drying oils,
and Cannabis-seed cake is a fine feed for ranch animals.
Higher-protein varieties may be developed for food. Also,
seeds are selected for rapid germination rate.
n) Maturation - Cannabis strains differ greatly as to when
they mature and how they respond to changing environ-
ment. Some strains, such as Mexican and Hindu Kush, are
famous for early maturation, and others, such as Colom-
bian and Thai, are stubborn in maturing and nearly always
finish late, if at all. Imported strains are usually character-
ized as either early, average, or late in maturing; however, a
particular strain may produce some individuals which ma-
ture early and others which mature late. Through selection,
breeders have, on the one hand, developed strains that
mature in four weeks, outdoors under temperate condi-
tions; and on the other hand, they have developed green-
house strains that mature in up to four months in their
protected environment. Early maturation is extremely ad-
vantageous to growers who live in areas of late spring and
early fall freezes. Consequently, especially early-maturing
plants are selected as parents for future early-maturing
strains.
o) Flowering - Once a plant matures and begins to bear
flowers it may reach peak floral production in a few weeks,
or the floral clusters may continue to grow and develop for
several months. The rate at which a strain flowers is inde-
pendent of the rate at which it matures, so a plant may
wait until late in the season to flower and then grow ex-
tensive, mature floral clusters in only a few weeks.
p) Ripening - Ripening of Cannabis flowers is the final
step in their maturation process Floral clusters will usually
mature and ripen in rapid succession, but sometimes large
floral clusters will form and only after a period of apparent
hesitation will the flowers begin to produce resin and ripen.
Once ripening starts it usually spreads over the entire
plant, but some strains, such as those from Thailand, are
known to ripen a few floral clusters at a time over several
months. Some fruit trees are similarly everbearing with a
yearlong season of production. Possibly Cannabis strains
could be bred that are true everbearing perennials that con-
tinue to flower and mature consistently all year long.
q) Cannabinoid Profile - It is supposed that variations in
the type of high associated with different strains of Canna-
bis result from varying levels of cannabinoids. THC is the
primary psychoactive ingredient which is acted upon syn-
ergistically by small amounts of CBN, CBD, and other
accessory cannabinoids. We know that cannabinoid levels
may be used to establish cannabinoid phenotypes and that
these phenotypes are passed on from parent to offspring.
Therefore, cannabinoid levels are in part determined by
genes. To accurately characterize highs from various indi-
viduals and establish criteria for breeding strains with par-
ticular cannabinoid contents, an accurate and easy method
is necessary for measuring cannabinoid levels in prospective
parents.
Various combinations of these traits are possible and
inevitable. The traits that we most often see are most likely
dominant and any effort to alter genetics and improve Can-
nab is strains are most easily accomplished by concentrating
on the major phenotypes for the most important traits. The
best breeders set high goals of a limited scope and adhere
to their ideals.
6. Gross Phenotypes of Cannabis Strains
The gross phenotype or general growth form is deter-
mined by size, root production, branching pattern, sex,
maturation, and floral characteristics. Most imported vari-
eties have characteristic gross phenotypes although there
tend to be occasional rare examples of almost every pheno-
type in nearly every variety. This indicates the complexity
of genetic control determining gross phenotype. Hybrid
crosses between imported pure varieties were the beginning
of nearly every domestic strain of Cannabis. In hybrid
crosses, some dominant characteristics from each parental
variety are exhibited in various combinations by the F1
offspring. Nearly all of the offspring will resemble both
parents and very few will resemble only one parent. This
sounds like it is saying a lot, but this F1 hybrid generation
is far from true-breeding and the subsequent F2 generation
will exhibit great variation, tending to look more like one
or the other of the original imported parental varieties, and
will also exhibit recessive traits not apparent in either of
the original parents. If the F1 offspring are desirable plants
it will be difficult to continue the hybrid traits in subse-
quent generations. Enough of the original F1 hybrid seeds
are produced so they may be used year after year to pro-
duce uniform crops of desirable plants.
Phenotypes and Characteristics
of Imported Strains
Following is a list of gross phenotypes and character-
istics for many imported strains of Cannabis.
1. Fiber Strain Gross Phenotypes (hemp
types)
2. Drug Strain Gross Phenotypes
a) Colombia - highland, lowland
(marijuana)
b) Congo - (marijuana)
c) Hindu Kush - Afghanistan and
Pakistan (hashish)
d) Southern India - (ganja marijuana)
e) Jamaica - Carribean hybrids
f) Kenya - Kisumu (dagga marijuana)
g) Lebanon - (hashish)
h) Malawi, Africa - Lake Nyasa (dagga
marijuana)
i) Mexico - Michoacan, Oaxaca,
Guerrero (marijuana)
j) Morocco - Rif mountains (kif
marijuana and hashish)
h) Nepal - wild (ganja marijuana and
hashish)
1) Russian - ruderalis (uncultivated)
m) South Africa - (dagga marijuana)
n) Southeast Asia - Cambodia, Laos,
Thailand, Vietnam (ganja marijuana)
3. Hybrid Drug Phenotypes
a) Creeper Phenotype
b) Huge Upright Phenotype
In general the F1 and F2 pure-bred offspring of these
imported varieties are more similar to each other than they
are to other varieties and they are termed pure strains.
However, it should be remembered that these are average
gross phenotypes and recessive variations within each trait
will occur. In addition, these representations are based on
unpruned plants growing in ideal conditions and stress will
alter the gross phenotype. Also, the protective environment
of a greenhouse tends to obscure the difference between
different strains. This section presents information that is
used in the selection of pure strains for breeding.
1. Fiber Strain Gross Phenotypes
Fiber strains are characterized as tall, rapidly matur-
ing, limbless plants which are often monoecious. This
growth habit has been selected by generations of fiber-
producing farmers to facilitate forming long fibers through
even growth and maturation. Monoecious strains mature
more evenly than dioecious strains, and fiber crops are
usually not grown long enough to set seed which interferes
with fiber production. Most varieties of fiber Cannabis orig-
inate in the northern temperate climates of Europe, Japan,
China and North America. Several strains have been
selected from the prime hemp growing areas and offered
commercially over the last fifty years in both Europe and
America. Escaped fiber strains of the midwestern United
States are usually tall, skinny, relatively poorly branched,
weakly flowered, and low in cannabinoid production. They
represent an escaped race of Cannabis sativa hemp. Most
fiber strains contain CBD as the primary cannabinoid and
little if any THC.
2. Drug Strain Gross Phenotypes
Drug strains are characterized by Delta1-THC as the pri-
mary cannabinoid, with low levels of other accessory can-
nabinoids such as THCV, CBD, CBC, and CBN. This results
from selective breeding for high potency or natural selec-
tion in niches where Delta1-THC biosynthesis favors survival.
a) Colombia - (0 to 10 north latitude)
Colombian Cannabis originally could be divided into
two basic strains: one from the low-altitude humid coastal
areas along the Atlantic near Panama, and the other from
the more arid mountain areas inland from Santa Marta.
More recently, new areas of cultivation in the interior
plateau of southern central Colombia and the highland
valleys stretching southward from the Atlantic coast have
become the primary areas of commercial export Cannabis
cultivation. Until recent years high quality Cannabis was
available through the black market from both coastal and
highland Colombia. Cannabis was introduced to Colombia
just over 100 years ago, and its cultivation is deeply rooted
in tradition. Cultivation techniques often involve trans-
planting of selected seedlings and other individual atten-
tion. The production of "la mona amarilla" or gold buds is
achieved by girdling or removing a strip of bark from the
main stem of a nearly mature plant, thereby restricting the
flow of water, nutrients, and plant products. Over several
days the leaves dry up and fall off as the flowers slowly die
and turn yellow. This produces the highly prized "Colom-
bian gold" so prevalent in the early to middle 1970s (Par-
tridge 1973). Trade names such as "punta roja" (red tips
[pistils] ), "Cali Hills," "choco," "lowland," "Santa Marta
gold," and "purple" give us some idea of the color of older
varieties and the location of cultivation.
In response to an incredible demand by America for
Cannabis, and the fairly effective control of Mexican Can-
nabis importation and cultivation through tightening bor-
der security and the use of Paraquat, Colombian farmers
have geared up their operations. Most of the marijuana
smoked in America is imported from Colombia. This also
means that the largest number of seeds available for domes-
tic cultivation also originate in Colombia. Cannabis agri-
business has squeezed out all but a few small areas where
labor-intensive cultivation of high quality drug Cannabis
such as "Ia mona amarilla" can continue. The fine mari-
juana of Colombia was often seedless, but commercial
grades are nearly always well seeded. As a rule today, the
more remote highland areas are the centers of commercial
agriculture and few of the small farmers remain. It is
thought that some highland farmers must still grow fine
Cannabis, and occasional connoisseur crops surface. The
older seeds from the legendary Colombian strains are now
highly prized by breeders. In the heyday of "Colombian
gold" this fine cerebral marijuana was grown high in the
mountains. Humid lowland marijuana was characterized by
stringy, brown, fibrous floral clusters of sedative narcotic
high. Now highland marijuana has become the commercial
product and is characterized by leafy brown floral clusters
and sedative effect. Many of the unfavorable characteristics
of imported Colombian Cannabis result from hurried com-
mercial agricultural techniques combined with poor curing
and storage. Colombian seeds still contain genes favoring
vigorous growth and high THC production. Colombian
strains also contain high levels of CBD and CBN, which
could account for sedative highs and result from poor cur-
mg and storage techniques. Domestic Colombian strains
usually lack CBD and CBN. The commercial Cannabis
market has brought about the eradication of some local
strains by hybridizing with commercial strains.
Colombian strains appear as relatively highly branched
conical plants with a long upright central stem, horizontal
limbs and relatively short internodes. The leaves are charac-
terized by highly serrated slender leaflets (7-11) in a
nearly complete to overlapping circular array of varying
shades of medium green. Colombian strains usually flower
late in temperate regions of the northern hemisphere and
may fail to mature flowers in colder climates. These strains
favor the long equatorial growing seasons and often seem
insensitive to the rapidly decreasing daylength during
autumn in temperate latitudes. Because of the horizon-
tal branching pattern of Colombian strains and their long
growth cycle, pistillate plants tend to produce many flow-
ering clusters along the entire length of the stem back to
the central stalk. The small flowers tend to produce small,
round, dark, mottled, and brown seeds. Imported and do-
mestic Colombian Cannabis often tend to be more sedative
in psychoactivity than other strains. This may be caused by
the synergistic effect of THC with higher levels of CBD or
CBN. Poor curing techniques on the part of Colombian
farmers, such as sun drying in huge piles resembling com-
post heaps, may form CBN as a degradation product of
THC. Colombian strains tend to make excellent hybrids
with more rapidly maturing strains such as those from
Central and North America.
b) Congo - (5 north to 5 south latitude)
Most seeds are collected from shipments of commer-
cial grade seeded floral clusters appearing in Europe.
c) Hindu Kush Range - Cannabis indica (Afghanistan and
Pakistan) - (30 to 37 north latitude)
This strain from the foothills (up to 3,200 meters
[10,000 feetj) of the Hindu Kush range is grown in small
rural gardens, as it has been for hundreds of years, and is
used primarily for the production of hashish. In these areas
hashish is usually made from the resins covering the pistil-
late calyxes and associated leaflets. These resins are re-
moved by shaking and crushing the flowering tops over a
silk screen and collecting the dusty resins that fall off the
plants. Adulteration and pressing usually follow in the pro-
duction of commercial hashish. Strains from this area are
often used as type examples for Cannabis indica. Early
maturation and the belief by clandestine cultivators that
this strain may be exempt from laws controlling Cannabis
sativa and indeed may be legal, has resulted in its prolifera-
tion throughout domestic populations of "drug" Cannabis.
Names such as "hash plant" and "skunk weed" typify its
acrid aroma reminiscent of "primo" hashish from the high
valleys near Mazar-i-Sharif, Chitral, and Kandahar in Af-
ghanistan and Pakistan.
This strain is characterized by short, broad plants with
thick, brittle woody stems and short internodes. The main
stalk is usually only four to six feet tall, but the relatively
unbranched primary limbs usually grow in an upright fash-
ion until they are nearly as tall as the central stalk and form
a sort of upside-down conical shape. These strains are of
medium size, with dark green leaves having 5 to 9 very
wide, coarsely serrated leaflets in a circular array. The
lower leaf surface is often lighter in color than the upper
surface. These leaves have so few broad coarse leaflets that
they are often compared to a maple leaf. Floral clusters are
dense and appear along the entire length of the primary
limbs as very resinous leafy balls. Most plants produce
flowering clusters with a low calyx-to-leaf ratio, but the
inner leaves associated with the calyxes are usually liber-
ally encrusted with resin. Early maturation and extreme
resin production is characteristic of these strains. This may
be the result of acclimatization to northern temperate lati-
tudes and selection for hashish production. The acrid smell
associated with strains from the Hindu Kush appears very
early in the seedling stage of both staminate and pistillate
individuals and continues throughout the life of the plant.
Sweet aromas do often develop but this strain usually loses
the sweet fragrance early, along with the clear, cerebral
psychoactivity.
Short stature, early maturation, and high resin pro-
duction make Hindu Kush strains very desirable for hybrid-
izing and indeed they have met with great popularity. The
gene pool of imported Hindu Kush strains seems to be
dominant for these desirable characteristics and they seem
readily passed on to the F1 hybrid generation. A fine hy-
brid may result from crossing a Hindu Kush variety with a
late-maturing, tall, sweet strain from Thailand, India, or
Nepal. This produces hybrid offspring of short stature, high
resin content, early maturation, and sweet taste that will
mature high quality flowers in northern climates. Many
hybrid crosses of this type are made each year and are
currently cultivated in many areas of North America.
Hindu Kush seeds are usually large, round, and dark grey
or black in coloring with some mottling.
d) India Centra1 Southern - Kerala, Mysore, and Madras
regions (10 to 20 north latitude)
Ganja (or flowering Cannabis tops) has been grown in
India for hundreds of years. These strains are usually grown
in a seedless fashion and are cured, dried, and smoked as
marijuana instead of being converted to hashish as in many
Central Asian areas. This makes them of considerable inter-
est to domestic Cannabis cultivators wishing to reap the
benefits of years of selective breeding for fine ganja by
Indian farmers. Many Europeans and Americans now live
in these areas of India and ganja strains are finding their
way into domestic American Cannabis crops.
Ganja strains are often tall and broad with a central
stalk up to 12 feet tall and spreading highly-branched limbs.
The leaves are medium green and made up of 7 to 11 leaf-
lets of moderate size and serration arranged in a circular
array. The frond-like limbs of ganja strains result from ex-
tensive compound branching so that by the time floral
clusters form they grow from tertiary or quaternary limbs.
This promotes a high yield of floral clusters which in ganja
strains tend to be small, slender, and curved. Seeds are
usually small and dark. Many spicy aromas and tastes occur
in Indian ganja strains and they are extremely resinous and
psychoactive. Medicinal Cannabis of the late 1800s and
early 1900s was usually Indian ganja.
e) Jamaica - (18 north latitude)
Jamaican strains were not uncommon in the late
1960s and early 1970s but they are much rarer today.
Both green and brown varieties are grown in Jamaica. The
top-of-the-line seedless smoke is known as the "lamb's
bread" and is rarely seen outside Jamaica. Most purported
Jamaican strains appear stringy and brown much like low-
land or commercial Colombian strains. Jamaica's close
proximity to Colombia and its position along the routes of
marijuana smuggling from Colombia to Florida make it
likely that Colombian varieties now predominate in Jamaica
even if these varieties were not responsible for the original
Jamaican strains. Jamaican strains resemble Colombian
strains in leaf shape, seed type and general morphology but
they tend to be a little taller, thinner, and lighter green.
Jamaican strains produce a psychoactive effect of a particu-
larly clear and cerebral nature, unlike many Colombian
strains. Some strains may also have come to Jamaica from
the Caribbean coast of Mexico, and this may account for
the introduction of cerebral green strains.
f) Kenya - Kisumu (5 north to 5 south latitude)
Strains from this area have thin leaves and vary in
color from light to dark green. They are characterized by
cerebral psychoactivity and sweet taste. Hermaphrodites
are common.
g) Lebanon - (34 north latitude)
Lebanese strains are rare in domestic Cannabis crops
but do appear from time to time. They are relatively short
and slender with thick stems, poorly developed limbs, and
wide, medium-green leaves with 5 to 11 slightly broad
leaflets. They are often early-maturing and seem to be quite
leafy, reflecting a low calyx-to-leaf ratio. The calyxes are
relatively large and the seeds flattened, ovoid and dark
brown in color. As with Hindu Kush strains, these plants
are grown for the production of screened and pressed
hashish, and the calyx-to-leaf ratio may be less important
than the total resin production for hashish making. Leban-
ese strains resemble Hindu Kush varieties in many ways
and it is likely that they are related.
h) Malawi, Africa - (10 to 15 south latitude)
Malawi is a small country in eastern central Africa
bordering Lake Nyasa. Over the past few years Cannabis
from Malawi has appeared wrapped in bark and rolled
tightly, approximately four ounces at a time. The nearly
seedless flowers are spicy in taste and powerfully psycho-
active. Enthusiastic American and European Cannabis cul-
tivators immediately planted the new strain and it has be-
come incorporated into several domestic hybrid strains.
They appear as a dark green, large plant of medium height
and strong limb growth. The leaves are dark green with
coarsely serrated, large, slender leaflets arranged in a nar-
row, drooping, hand-like array. The leaves usually lack
serrations on the distal (tip portion) 20% of each leaflet.
The mature floral clusters are sometimes airy, resulting
from long internodes, and are made up of large calyxes
and relatively few leaves. The large calyxes are very sweet
and resinous, as well as extremely psychoactive. Seeds are
large, shortened, flattened, and ovoid in shape with a dark
grey or reddish brown, mottled perianth or seed coat. The
caruncle or point of attachment at the base of the seed is
uncommonly deep and usually is surrounded by a sharp-
edged lip. Some individuals turn a very light yellow green
in the flowering clusters as they mature under exposed
conditions. Although they mature relatively late, they do
seem to have met with acceptance in Great Britain and
North America as drug strains. Seeds of many strains appear
in small batches of low-quality African marijuana easily
available in Amsterdam and other European cities. Pheno-
types vary considerably, however, many are similar in
appearance to strains from Thailand.
i) Mexico - (15 to 27 north latitude)
Mexico had long been the major source of marijuana
smoked in America until recent years. Efforts by the border
patrols to stop the flow of Mexican marijuana into the
United States were only minimally effective and many vari-
eties of high quality Mexican drug Cannabis were continu-
ally available. Many of the hybrid strains grown domestic-
ally today originated in the mountains of Mexico. In
recent years, however, the Mexican government (with mone-
tary backing by the United States) began an intensive pro-
gram to eradicate Cannabis through the aerial spraying of
herbicides such as Paraquat. Their program was effective,
and high quality Mexican Cannabis is now rarely available.
It is ironic that the NIMH (National Institute of Mental
Health) is using domestic Mexican Cannabis strains grown
in Mississippi as the pharmaceutical research product for
chemotherapy and glaucoma patients. In the prime of
Mexican marijuana cultivation from the early 1960s to the
middle 1970s, strains or "brands" of Cannabis were usually
affixed with the name of the state or area where they were
grown. Hence names like "Chiapan," "Guerreran," "Nay-
arit," "Michoacan," "Oaxacan," and "Sinaloan" have geo-
graphic origins behind their common names and mean
something to this very day. All of these areas are Pacific
coastal states extending in order from Sinaloa in the north
at 27; through Nayarit, Jalisco, Michoacan, Guerrero, and
Oaxaca; to Chiapas in the south at 15 - All of these states
stretch from the coast into the mountains where Cannabis
is grown.
Strains from Michoacan, Guerrero, and Oaxaca were
the most common and a few comments may be ventured
about each and about Mexican strains in general.
Mexican strains are thought of as tall, upright plants
of moderate to large size with light to dark green, large
leaves. The leaves are made up of long, medium width,
moderately serrated leaflets arranged in a circular array.
The plants mature relatively early in comparison to strains
from Colombia or Thailand and produce many long floral
clusters with a high calyx-to-leaf ratio and highly cerebral
psychoactivity. Michoacan strains tend to have very slender
leaves and a very high calyx-to-leaf ratio as do Guerreran
strains, but Oaxacan strains tend to be broader-leafed,
often with leafier floral clusters. Oaxacan strains are gener-
ally the largest and grow vigorously, while Michoacan
strains are smaller and more delicate. Guerreran strains are
often short and develop long, upright lower limbs. Seeds
from most Mexican strains are fairly large, ovoid, and
slightly flattened with a light colored grey or brown, un-
mottled perianth. Smaller, darker, more mottled seeds
have appeared in Mexican marijuana during recent years.
This may indicate that hybridization is taking place in
Mexico, possibly with introduced seed from the largest
seed source in the world, Colombia. No commercial seeded
Cannabis crops are free from hybridization and great varia-
tion may occur in the offspring. More recently, large
amounts of hybrid domestic seed have been introduced
into Mexico. It is not uncommon to find Thai and Afghani
phenotypes in recent shipments of Cannabis from Mexico.
j) Morocco, Rif Mountains - (35 north latitude)
The Rif mountains are located in northernmost
Morocco near the Mediterranean Sea and range up to
2,500 meters (8,000 feet). On a high plateau surrounding
the city of Ketama grows most of the Cannabis used for
kif floral clusters and hashish production. Seeds are broad-
sown or scattered on rocky terraced fields in the spring, as
soon as the last light snows melt, and the mature plants are
harvested in late August and September. Mature plants are
usually 1 to 2 meters (4 to 6 feet) tall and only slightly
branched. This results from crowded cultivation tech-
niques and lack of irrigation. Each pistillate plant bears
only one main terminal flower cluster full of seeds. Few
staminate plants, if any, are pulled to prevent pollination.
Although Cannabis in Morocco was originally cultivated for
floral clusters to be mixed with tobacco and smoked as
kif, hashish production has begun in the past 30 years due
to Western influence. In Morocco, hashish is manufactured
by shaking the entire plant over a silk screen and collecting
the powdery resins that pass through the screen. It is a
matter of speculation whether the original Moroccan kif
strains might be extinct. It is reported that some of these
strains were grown for seedless flower production and areas
of Morocco may still exist where this is the tradition.
Because of selection for hashish production, Moroccan
strains resemble both Lebanese and Hindu Kush strains in
their relatively broad leaves, short growth habit, and high
resin production. Moroccan strains are possibly related to
these other Cannabis indica types.
k) Nepal - (26 to 30 north latitude)
Most Cannabis in Nepal occurs in wild stands high in
the Himalayan foothills (up to 3,200 meters [10,000
feet]). Little Cannabis is cultivated, and it is from select
wild plants that most Nepalese hashish and marijuana ori-
ginate. Nepalese plants are usually tall and thin with long,
slightly branched limbs. The long, thin flowering tops are
very aromatic and reminiscent of the finest fresh "temple
ball" and "finger" hashish hand-rubbed from wild plants.
Resin production is abundant and psychoactivity is high
Few Nepalese strains have appeared in domestic Cannabis
crops but they do seem to make strong hybrids with strains
from domestic sources and Thailand.
I) Russian - (35 to 60 north latitude) Cannabis ruderalis
(uncultivated)
Short stature (10 to 50 centimeters [3 to 18 inches])
and brief life cycle (8 to 10 weeks), wide, reduced leaves
and specialized seeds characterize weed Cannabis of Russia.
Janischewsky (1924) discovered weedy Cannabis and
named it Cannabis ruderalis. Ruderalis could prove valuable
in breeding rapidly maturing strains for commercial use in
temperate latitudes. It flowers when approximately 7 weeks
old without apparent dependence on daylength. Russian
Cannabis ruderalis is nearly always high in CBD and low
in THC.
m) South Africa - (22 to 35 south latitude)
Dagga of South Africa is highly acclaimed. Most seeds
have been collected from marijuana shipments in Europe.
Some are very early-maturing (September in northern lati-
tudes) and sweet smelling. The stretched light green floral
clusters and sweet aroma are comparable to Thai strains.
n) Southeast Asia - Cambodia, Laos, Thailand and Viet-
nam (10 to 20 north latitude)
Since American troops first returned from the war in
Vietnam, the Cambodian, Laotian, Thai, and Vietnamese
strains have been regarded as some of the very finest in the
world. Currently most Southeast Asian Cannabis is pro-
duced in northern and eastern Thailand. Until recent times,
Cannabis farming has been a cottage industry of the north-
ern mountain areas and each family grew a small garden.
The pride of a farmer in his crop was reflected in the high
quality and seedless nature of each carefully wrapped Thai
stick. Due largely to the craving of Americans for exotic
marijuana, Cannabis cultivation has become a big business
in Thailand and many farmers are growing large fields of
lower quality Cannabis in the eastern lowlands. It is sus-
pected that other Cannabis strains, brought to Thailand to
replenish local strains and begin large plantations, may have
hybridized with original Thai strains and altered the resul-
tant genetics. Also, wild stands of Cannabis may now be
cut and dried for export.
Strains from Thailand are characterized by tall mean-
dering growth of the main stalk and limbs and fairly exten-
sive branching. The leaves are often very large with 9 to 11
long, slender, coarsely serrated leaflets arranged in a droop-
ing hand like array. The Thai refer to them as "alligator
tails" and the name is certainly appropriate.
Most Thai strains are very late-maturing and subject
to hermaphrodism. It is not understood whether strains
from Thailand turn hermaphrodite as a reaction to the ex-
tremes of northern temperate weather or if they have a
genetically controlled tendency towards hermaphrodism.
To the dismay of many cultivators and researchers, Thai
strains mature late, flower slowly, and ripen unevenly.
Retarded floral development and apparent disregard for
changes in photoperiod and weather may have given rise to
the story that Cannabis plants in Thailand live and bear
flowers for years. Despite these shortcomings, Thai strains
are very psychoactive and many hybrid crosses have been
made with rapidly maturing strains, such as Mexican and
Hindu Kush, in a successful attempt to create early-
maturing hybrids of high psychoactivity and characteristic
Thai sweet, citrus taste. The calyxes of Thai strains are very
large, as are the seeds and other anatomical features, lead-
ing to the misconception that strains may be polyploid. No
natural polyploidy has been discovered in any strains of
Cannabis though no one has ever taken the time to look
thoroughly. The seeds are very large, ovoid, slightly flat-
tened, and light brown or tan in color. The perianth is
never mottled or striped except at the base. Greenhouses
prove to be the best way to mature stubborn Thai strains
in temperate climes.
3. Hybrid Drug Phenotypes
a) Creeper Phenotype - This phenotype has appeared in
several domestic Cannabis crops and it is a frequent pheno-
type in certain hybrid strains. It has not yet been deter-
mined whether this trait is genetically controlled (domi-
nant or recessive), but efforts to develop a true-breeding
strain of creepers are meeting with partial success. This
phenotype appears when the main stalk of the seedling has
grown to about 1 meter (3 feet) in height. It then begins to
bend at approximately the middle of the stalk, up to 700
from the vertical, usually in the direction of the sun. Sub-
sequently, the first limbs sag until they touch the ground
and begin to grow back up. In extremely loose mulch and
humid conditions the limbs will occasionally root along the
bottom surface. Possibly as a result of increased light expo-
sure, the primary limbs continue to branch once or twice,
creating wide frond-like limbs of buds resembling South
Indian strains. This phenotype usually produces very high
flower yields. The leaves of these creeper phenotype plants
are nearly always of medium size with 7-11 long, narrow,
highly serrated leaflets.
b) Huge Upright Phenotype - This phenotype is character-
ized by medium size leaves with narrow, highly serrated
leaflets much like the creeper strains, and may also be an
acclimatized North American phenotype. In this pheno-
type, however, a long, straight central stalk from 2 to 4
meters (6.5 to 13 feet) tall forms and the long, slender
primary limbs grow in an upright fashion until they are
nearly as tall or occasionally taller than the central stalk.
This strain resembles the Hindu Kush strains in general
shape, except that the entire domestic plant is much larger
than the Hindu Kush with long, slender, more highly
branched primary limbs, much narrower leaflets, and a
higher calyx-to-leaf ratio. These huge upright strains are
also hybrids of many different imported strains and no
specific origin may be determined.
The preceding has been a listing of gross phenotypes
for several of the many strains of Cannabis occurring world-
wide. Although many of them are rare, the seeds appear
occasionally due to the extreme mobility of American and
European Cannabis enthusiasts. As a consequence of this
extreme mobility, it is feared that many of the world's
finest strains of Cannabis have been or may be lost forever
due to hybridization with foreign Cannabis populations and
the socio-economic displacement of Cannabis cultures
worldwide. Collectors and breeders are needed to preserve
these rare and endangered gene pools before it is too late.
Various combinations of these traits are possible and
inevitable. The traits that we most often see are most likely
dominant and the improvement of Cannabis strains through
breeding is most easily accomplished by concentrating on
the dominant phenotypes for the most important traits.
The best breeders set high goals of limited scope and ad-
here to their ideals.
