here's an excerpt from Rober Clarks book Marijuana Botany
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 transplanting of selected seedlings and other individual attention. 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 "Colombian gold" so prevalent in the early to middle 1970s (Partridge 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 Cannabis importation and cultivation through tightening border 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 marijuana 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 commercial 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 curing 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 characterized 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 horizontal branching pattern of Colombian strains and their long growth cycle, pistillate plants tend to produce many flowering 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 domestic 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.