24 hour light vs. 18/6.

hm. will be trying this next veg.

Plants perform different numbers of functions to differing degrees depending on it being during hours of light or hours of darkness. During hours of light the plant will take in as much light to use to create energy as it can, but it is limited so the total amount of energy to rely on is also limited. Plants allocate certain amounts of energy for different functions and during hours of daylight they perform most plant functions so each function receives its portion of the overall amount of energy, which can be small.

During hours of darkness most plant functions are cut back or stopped and the plant operates on stored energy, as if it has rechargeable batteries for night use. To maximize its stored energy use all energy is allocated to a limited number of functions compared to the number of functions occurring during hours of light. Certain plant functions will be allocated increased amounts of energy during hours of darkness above that which they receive during hours of light. There are various reasons behind how what is done and when and in what amount and why but basically the most important plant functions at that stage of growth receive the largest allocation of power nightly.

Have you ever noticed that over an entire day while you might see growth if you check your plants several times in a day it is not much but it is not uncommon to check them first thing in the morning and think, Holy Hannah, I have to raise my light .. those things grew like weeds last night. A plant is allocated more energy for growth during hours of darkness than they are during hours of light. People tend to believe it is just because they were asleep and not looking often enough to not notice the growth so when it is all seen at once in the morning naturally it seems like a lot. But that is not the biggest part of why. It factors in slightly but it is mostly because that is when plants have the needed energy to grow that fast.

Another key night function, during flower and more and more important as it goes on, is the rate of THC production increases at night, increased amounts of energy are allocated to THC production during hours of darkness than during hours of light. Put very basically THC works like sunscreen within the heads of THC producing trichomes. It protects the delicate inner workings of the trichome-head. That means that while some THC is produced during the day, due to low energy allocation there is a net loss of THC for the day, more is degraded by light rays than is created. During hours of darkness energy allocation for THC is a priority and enough THC is made to replace what was lost and then an additional amount and over time you have a slow steady increase it total amount, and then you just have to pick the right time to chop and you’re in like Flynn. But it is during those hours of darkness when the true slow but steady overall increase of THC actually occurs.

Speedier/increased root growth has been mentioned, and that as has been said means stronger healthier more vibrant plants and it is another example of what plants do and when and how lighting will effect or alter what they can and will do.

Plants lived in conditions of light and dark for ages and ages and they pretty much grew accustomed to how to use the different periods to their best advantage, since it was of course they best they had to work with, and they figured things out pretty well for themselves all on their own. Normally when people try to fiddle with certain things like light and dark and amounts of each, once past a certain point they might believe they see a gain, even when one is not there to be seen, but there is almost certainly a loss they are failing to see exists.

Brick Top said:

Plants lived in conditions of light and dark for ages and ages and they pretty much grew accustomed to how to use the different periods to their best advantage, since it was of course they best they had to work with, and they figured things out pretty well for themselves all on their own. Normally when people try to fiddle with certain things like light and dark and amounts of each, once past a certain point they might believe they see a gain, even when one is not there to be seen, but there is almost certainly a loss they are failing to see exists.

Click to expand...

thanks for the info

Brick Top said:

Plants perform different numbers of functions to differing degrees depending on it being during hours of light or hours of darkness. During hours of light the plant will take in as much light to use to create energy as it can, but it is limited so the total amount of energy to rely on is also limited. Plants allocate certain amounts of energy for different functions and during hours of daylight they perform most plant functions so each function receives its portion of the overall amount of energy, which can be small.

During hours of darkness most plant functions are cut back or stopped and the plant operates on stored energy, as if it has rechargeable batteries for night use. To maximize its stored energy use all energy is allocated to a limited number of functions compared to the number of functions occurring during hours of light. Certain plant functions will be allocated increased amounts of energy during hours of darkness above that which they receive during hours of light. There are various reasons behind how what is done and when and in what amount and why but basically the most important plant functions at that stage of growth receive the largest allocation of power nightly.

Have you ever noticed that over an entire day while you might see growth if you check your plants several times in a day it is not much but it is not uncommon to check them first thing in the morning and think, Holy Hannah, I have to raise my light .. those things grew like weeds last night. A plant is allocated more energy for growth during hours of darkness than they are during hours of light. People tend to believe it is just because they were asleep and not looking often enough to not notice the growth so when it is all seen at once in the morning naturally it seems like a lot. But that is not the biggest part of why. It factors in slightly but it is mostly because that is when plants have the needed energy to grow that fast.

Another key night function, during flower and more and more important as it goes on, is the rate of THC production increases at night, increased amounts of energy are allocated to THC production during hours of darkness than during hours of light. Put very basically THC works like sunscreen within the heads of THC producing trichomes. It protects the delicate inner workings of the trichome-head. That means that while some THC is produced during the day, due to low energy allocation there is a net loss of THC for the day, more is degraded by light rays than is created. During hours of darkness energy allocation for THC is a priority and enough THC is made to replace what was lost and then an additional amount and over time you have a slow steady increase it total amount, and then you just have to pick the right time to chop and you’re in like Flynn. But it is during those hours of darkness when the true slow but steady overall increase of THC actually occurs.

Speedier/increased root growth has been mentioned, and that as has been said means stronger healthier more vibrant plants and it is another example of what plants do and when and how lighting will effect or alter what they can and will do.

Plants lived in conditions of light and dark for ages and ages and they pretty much grew accustomed to how to use the different periods to their best advantage, since it was of course they best they had to work with, and they figured things out pretty well for themselves all on their own. Normally when people try to fiddle with certain things like light and dark and amounts of each, once past a certain point they might believe they see a gain, even when one is not there to be seen, but there is almost certainly a loss they are failing to see exists.

Click to expand...

That was an amazing monologue. Thank you. No really,I am not being a smart ass.Chalked full of useful information.

I do an 18/6 myself, always have.

But, if you're feeling 'wild and crazy', you could give 20/4 a shot.

Have heard it's an excellent compromise, but I'm too lazy to reset my timers. LOL

Wet

Hey Brick top I gave you rep because that last post of yours was so great! Question though: Based off what you said do you think that harvesting after say 36 or 48 hours of darkness would be beneficial? I know the plant would used its stored energy for more thc and such, would it also eat itself alive to put off as much THC and trichomes as it could before it died of lack of light? Or would one be better off just harvesting before the light comes on after a normal dark period?

PS: do you know about any non 24 hour cycles? Like people who talk about 10 12 10 12 or weird stuff like that? Any thoughts on what say 10/10 would do vs 12/12?

jdizzle22 said:

Hey Brick top I gave you rep because that last post of yours was so great! Question though: Based off what you said do you think that harvesting after say 36 or 48 hours of darkness would be beneficial? I know the plant would used its stored energy for more thc and such, would it also eat itself alive to put off as much THC and trichomes as it could before it died of lack of light? Or would one be better off just harvesting before the light comes on after a normal dark period?

PS: do you know about any non 24 hour cycles? Like people who talk about 10 12 10 12 or weird stuff like that? Any thoughts on what say 10/10 would do vs 12/12?

Click to expand...

While some people have questioned the test results because some years later the group was caught padding some other results, tests, accurate or not I cannot swear, have shown that giving plants 72-hours of total darkness at the end of flower/just prior to harvest can increase levels/amounts of THC in some strains as much as 30%.

The THC itself is not more potent by volume but supposedly you can have a large increase in volume.

It is only my opinion, since people have questioned the research and as far as I know no one else has tried to duplicate it or disprove it, they just questions it … but considering how certain light rays and THC react together it would make sense that they should at least in most cases be some increase in overall THC.

It is the same principal as when you know you will be harvesting tomorrow when your lights turn off tonight you unplug them or flip a switch, if you have then switched, so they do not turn on again tomorrow before you begin your harvest. Or in the case of an outside grower harvesting at first light.

Either way the idea is to harvest without light rays having a chance to degrade any of the THC that was produced the night before.

Plants will only continue to perform their functions/live for a fairly short period of time once they are deprived of light but during that time they will continue their hours of darkness functions as much as they can for as long as they can. That would have to at the very least result in maximized levels of THC if not increased levels of THC, possibly as much as the tested/reports 30% increase certain strains developed. Genetics are bound to play anything from a small part to a major part in results but at least to some degree it has to happen.

Some people that swear outdoor grown pot is better will at times point to the length of the nights and the shortness of the days towards the end of flower and say look at how much more potent they became in the last weeks during the longest nights. They will say because of the extended period of time for THC production at maximum levels with the least amount of THC degrading per 24-hour period due to short days with the light rays striking the plants at lower angles the increased levels of THC late in flower was at least in part due to growing conditions and not only or even mostly plant genetics.


The same people will sometimes say the reason indoor growers try to stick with light cycles that make use of the longest period of light possible at any stage of growth is because they need to make up for the weakness of indoor lighting in comparison to the sun and think that will go a long way to make up for the difference but end up giving up quality by trying to find it. They think the natural lighting periods should be closer mimicked. I cannot say I agree with that, at least not all of it, but there is some logic to be found in parts of it.

Where I question that belief is if you are working with far less light than the sun supplies cutting the periods of light to more closely duplicate nature you are just giving your plants even less of the lower levels of light. How much of a loss might be the result? The other part is certain light rays so breakdown THC but then growing in conditions with much lower levels of those light rays, as in when growing inside rather than outside, how much less THC is degraded in an average day compared to when grown outside and is there more of a net gain found in one than the other? Will less be degraded so your overall gradual increase results in more or will along with the increased degrading process in outdoor growing will the light says stimulate the trichome heads to further increase THC, and other cannabinoid production, and there will be a larger net gain found there?

If anyone has performed definitive tests I have never read the results so it is sort of an opinion thing right now, so each person believes what they are most comfortable with.

I tend to believe that a 72-hour period of darkness just prior to harvest of an indoor crop and the longer fall nights and shorter fall days with sun lays striking plants from lower angles both cause an increase in THC production. In some strains the difference might be so slight that it would take the highest tech testing equipment to prove it and on another it might only take one hit of each test group type to make it clear.

In some cases genetics have a much greater or much lesser impact on the results of some method of growing. It just depends on what something is made up of and in what amounts as to if it will respond the same or better/more, less/worse for any growing method or trick.

There are a number of differing beliefs about various light cycles but I do not know of any that are out of the norm that have legitimate research behind them backing that the overall final results are better. People attempt various things and their observations tell them they see some positive or some negative and then they either go with it or not.

It is just what is observable and what is not and what people are unable to test but instead at best can only rely on senses to judge, which can be bent/formed by preconceptions, it is not all that uncommon for people to believe they found positive things that do not really exist and fail to find negative things that do exist.

The most standard indoors light cycle will most consistently provide the best results for the widest range of genetics and is the simplest, of course autoflower strains would add more to discuss, but in general it is the best and that is why it is the most used.

It is not that I have some problem in attempting to advance the science/art of herb growing through experimentation but I think that is best left for the pros to do and then instruct us on. They have the setups and the resources and if something turns out to be a flop they really aren’t out much but if we try something and it blows chunks, well a harvest celebration might not be much of a celebration now and then. So we can lose big.

Something I have said many times is that ever generation thinks that if it did not actually invent sex, drugs and rock & roll they at least perfected it. Something similar happens with each generation of growers. They get some Ralph Kramden super-idea and get all pumped up about it or hear of someone else’s idea or way of doing things and get all pumped up about it and they mention it in a thread and 30 people respond saying how great of an idea it is and how they will have to try it too.

I normally tend to chuckle because I can remember back to the 70’s and 80’s and 90’s when I tried those things or friends tried those things, or even older growers from the 60’s and maybe before had told me how they tried those things and in each case where there was no scientific research backing a final decision things were clear enough to say success or failure.

The successes were copied by virtually everyone but every generation of new growers will reinvent at least some of the failures and then get others whipped up on them and then they try them too …. and get the same basic poor results as in the 60’s and 70’s and 80’s and 90’s when the same things were attempted.

If a majority of skilled growers do something a certain way there is a valid reason behind it. It is because doing whatever it is in that way works the best overall.

Ok that was a good read with some good sentences! So if I got it right for indoors at least, that going 24-72 hours of darkness before harvest probably isn't worth it with most strains since there is little evidence of the effects of this? And that you don't recommend any kind of light schedule that doesn't run on 24 hour days/cycles?

I've been split on giving them extended darkness before harvest (since I've only read it works with 'white' strains and I have bag seed), if I do end up doing it, I will probably only go for a 36 hour period (turn the light off for good one night, harvest a couple mornings later). Presently I am thinking I won't do it... Who knows...

i have used all types of lighting times during my veg, i was just trying different things out, i noticed that they grew good for a little while under 24/0, but as time went on they began to look weak. under 18/6 they did well, the growth was not as fast as 24/0 but it did not seem to be stressing the plant. i found that my plants grew really well under 20/4, they grew just as fast as they did under 24 but with no stress

jdizzle22 said:

Ok that was a good read with some good sentences! So if I got it right for indoors at least, that going 24-72 hours of darkness before harvest probably isn't worth it with most strains since there is little evidence of the effects of this? And that you don't recommend any kind of light schedule that doesn't run on 24 hour days/cycles?

I've been split on giving them extended darkness before harvest (since I've only read it works with 'white' strains and I have bag seed), if I do end up doing it, I will probably only go for a 36 hour period (turn the light off for good one night, harvest a couple mornings later). Presently I am thinking I won't do it... Who knows...

Click to expand...

"The Stichting Institute of Medical marijuana (SIMM), the first company to sell marijuana through the pharmacies of Holland, has been investigating the medical possibilities of cannabis, together with TNO laboratories and the University of Leiden. One of their discoveries has been that to keep the ripe plants in the dark before harvesting could increase their potency.

SIMM’s growers separated a crop of mature plants, harvested half of them and kept the other half in absolute darkness for 72 hours before cutting and drying. Analysis of the resulting dried buds showed that some varieties had seen an increase of THC of up to 30%, while CBD and CBN remained the same."


I have never read what percentage of strains will respond and what percentage of strains will respond as much as 30% so I do not know what sort of gain you might see but for many years some very good growers have finished their plants in 72-hours of darkness, or in some cases less and in some cases more. At some point in time growers discovered that darkness increases THC levels and if nothing else a person should harvest just before first light, if growing outdoors, or if indoors, turn off their timers so the lights do not come on the next day before they get a chance to harvest their plants.

It only makes sense though. During the day plants multifunction, they perform many tasks at one time. Since a plant's ability to absorb light and create energy is limited plants allocate certain amounts of energy to various functions according to importance. During hours of light THC is broken down by light rays and during hours of darkness the lost THC is replaced and additional is made so there is a slow gradual increase in levels of THC during flower up until harvest.

During hours of light THC production is allocated less energy than it is during hours of darkness. Both growth and THC production receive more energy during hours of darkness than they do during hours of light. Other less important plant functions are stopped and others that are needed but are less important receive less energy than they would during hours of light.

People will say that plants "sleep" but plants are 24-hour a day operations. They just do things different during hours of light and darkness.

So .... what do you have to lose by finishing your plants in at least some extended period of darkness? You do not have the time to finish them so if you can pick up something by using darkness you would not be risking the loss of much if anything at all. Even if the strain is not one that will respond with a 30% increase, if you only end up with a 2% or a 5% or a 10% increase that would be well worth it at this point. If you do not get any increase you would still likely not really lose much if anything at all at this point.

You want to harvest before your lights come on so your plants should finish in darkness all the time anyway, even if only 12 hours. Since THC production has more energy during hours of darkness I would take advantage of that fact and attempt to make the most of it.

Are you much of a gambler? If so ... step up to the table and place your bet ............... and remember, "What transpires within the confines of the walls of Sodom, stays within the confines of the walls of Sodom." At my age that seems to fit better than "Remember, what happens in Vegas stays in Vegas." The other is more my era.

If you folks are really lucky one day I will tell you all Moses' trick to part the Red Sea. That Moses, he was such a practical joker! Once he toked some good herb there was no stopping the guy.

I clone 24/7 to this day ,in the past used to veg 24/7 ,then ran into unexplained issues so started vegging under 20/4 and made for much happier plants,and 18/6 works great aswell..

24/7 vegging from my experience can cause undo stress to the plant ..although some people have good luck it ,as a Med grower I veg for longer periods of time ,larger plants with low plant numbers.that may play a role aswell,someone who only veg's for a week or so after rooting could probably never see a problem with 24/7 vegging..but for my situation is unhealthy for the plants

besides rooting under 24/7 ,doing a re-veg on a plant is the only other reason I've found to use 24/7 lighting ,and even a after 2weeks of that I've had the best luck dropping it back to 20/4

Harvesting lights on/lights off is only a pleasure a personal grower can experience..when your a one man show chopping down multiple pounds of meds ,you have no choice..but personally I have never seen a noticeable difference in the quality of bud harvested lights on/off or sitting in the dark for a couple days

I would think the drying process would play a WAY bigger role in the finished product,but that's another thread in itself

lots of good thoughts in here

ive did grows at both light cycles.. and i deff prefer 18-6.. although i have heard some people say its good to stay on 24-0 for hte 1st week or 2.. but then to switch to 18-6.. never tried that.. i agree that all plants need a rest at some point. an dhave heard that wen the lights r on.. the leaves/buds grow.. and at night... thats wen the roots do the growing.. soo in order to have a healthy root structure.. u must keep the lights off for a little while at least

I'm growing on 24/0 right now with CFL's you don't use nearly as much energy. More light more bud.

yeah to reiterate; to pop seeds do 24/0. vegging do 20/4 or 18/6 (20/4 imo is better but do what you want)

then 12/12 for flowering. some people might argue to do like 14/10 or 13/11 cause more light(energy) more bud, but your plants are still getting energy(food) from just chillin so you dont have to overcompensate on the lights. plus whacky schedules can hermie a plant.

i guess its all up to the person, do what fits you best, smoke that herb

Personally I have found that leaving the lights on all the time just isn't worth it. For me, it raises the hermaphrodite rate and the extra little bit of growth you might gain can be overcome with some tactical pruning. 18/6 also provides a little bit of a buffer in that if you lose power on a 24 hour schedule you get darkness that could really throw off your plants. If you lose power on an 18/6 then there is a 25% chance it will happen at night and if the lights go out an extra hour or two early or stay off for an hour or two longer then you probably won't see any ill effects. That means you have a ten hour window to lose power and not suffer as horribly as you might otherwise. The power bill is another issue. For small ops it's not a big deal, but when you are already trying to manage a warehouse with 100k watt hours daily, shaving off an extra thousand dollars from your veg room starts to sound like a really good idea. I'm not trying to bash anybody's system or say anyone is wrong. Both ways work and arguments can be made for either side. These are just my thoughts and opinions, and in my opinion, I'd rather keep the thousand dollars every month and prune a little more.

I would like to clarify all the urban legends and old lady tales about 24/0 versus including some dark periods in your grow.

I will keep this simple because many come to these forums for guidance.

First off, For all beginners, the sole practical differences between 24/0 versus 18/6 are time and money. and if you are like me, time is money. I run 4 1000 watt lamps 2 in 2 8x 8 rooms and each increase my electric bill by $50. I do not run AC, but each lamp has its dedicated cooling fan and exhaust fan circuit. I run a humidifier hooked to the humidity port of the Environmental Controller in each room.

I journal each crop from seed to harvest. i measure height (growth rate) of each plant every 3 days(or watering) until i begin LST. There is on average 25% - 35% faster growth with 24/0 light than 18/6 depending on Sativa dominance or Indica dominance in the plant genetics. With 24/0, I shave my time to harvest by 25-30%. that is, i harvest 2-3 weeks quicker. Do the math and compare what you are really spending with the daily savings in 6 hours of darkness versus the savings at zero darkness. At 18/6 your overall electric bill is higher per crop. You spend more time on each crop (what do you consider your hourly wage?). And then there is the opportunity cost that comes with not having the product ready "in time"

Now for the science: on earth we have 3 major types of plants based on how they "cook" or "fix" Carbon(that means separate Carbon from CO2 and make sugar). They are C3 carbon fixation plants like Cannabis and C4 carbon fixation plants like corn, sugar cane and crab grass. Then there are Crassulacean Acid Metabolism (CAM) plants like cactus .

C3 fixation (C3 plants) thrive in areas where sunlight intensity is moderate, temperatures are moderate, carbon dioxide concentrations are moderate and groundwater is plentiful. The C3 plants can be considered Plant 1.0 compared to C4 plants. they (C3 plants) predate the C4 plants on the evolutionary scale. In dry areas, C3 plants shut their stomata to reduce water loss, but this stops CO2 from entering the leaves

Also we must clarify a common misconception in early academia (high school and freshman botany), that the ‘‘dark reactions’’ of the Calvin cycle (photosynthesis) actually occur in the dark. Truly it is called "dark reaction" because it takes place independent of the "immediate" presence of light energy. But because several enzymes in the so-called ‘‘dark reactions’’ are actually indirectly dependent on the presence of light for their activity, this "dark reaction" actually takes place 34/7 /365 regardless if it is a C3 or C4 plant and either plant does "feed continuously under uninterrupted light.

This is where c4 plants like sugar cane, corn and crab grass kick ass, they have evolved from c3 plants and have no limit to the intensity of light you throw at them. They simply keep pumping out sugars. Under dry hot conditions C3 plants shut their stomata to reduce water loss, this stops CO2 from entering the leaves to prevent photorespiration. But, this evolutionary advantage of c4 plants comes with an energy sink and that is why C3 plants will always outperform C4 plants if there is a lot of water and sun.

The sole purpose of a 12 hour dark time is to trigger flowering. The apparent growth or stretching you see is the plant using up resources (sugars) made during veg. during this phase the source for resources for other plant functions are reversed (leaves as source of sugars instead of roots) by the plant being in the dark for 12 hours.

NOW THIS IS WHERE MR / MRS SCIENCE TEACHER OR PROFESSOR "CALLED CANCER A DISEASE" instead of a condition because he/she did not know or thought students are not ready for the complex truth:

There is a third group of plants, the Crassulacean Acid Metabolism (CAM) plants, that survive in arid (dry) environments by opening their stomata only in the dark instead of the light, as do C3 and C4 plants. CAM plants only open Stomata at night to collection and fix CO2 in the dark. the stomata in the leaves remain shut during the day to reduce evapotranspiration. Examples are Aloe, Yucca(not to be confused with manihot/cassava), pineapple cactus etc.

by the way, several lab studies show that in cannabis;


The rate of photosynthesis and water use efficiency increased with light intensities at lower temperatures (20-25 °C)68-77F at 55% relative humidity and the maximum rate of photosynthesis in three university studies I came across was between 28-30 °C or 82.4 and 86F and under 1500 μmol of CO2 anything higher resulted in photorespiration (bad).

Nota Bene: In plants such as MJ, during the plant's growth period, usually during the spring or veg phase, storage organs such as the roots are sugar sources and leaves use up the sugars. After the growth period, when the meristems are dormant or when we induce flowering, the leaves become sources of sugar, and storage organs or roots become sinks. Developing seed-bearing organs (such as flowers) are always sinks. (this why it is critical to minimize leaf trimming once you induce flowering. It has not only been shown that via their roots, vascular plants actually absorb sucrose, glucose and fructose via processes of translocation, active transport, phloem loading and unloading. Cells in a sugar source or roots "load" a sieve-tube element by actively transporting solute molecules into it. This causes water to move into the sieve-tube element by osmosis, creating pressure that pushes the sap down the tube. In sugar sinks, cells actively transport solutes out of the sieve-tube elements, producing the exactly opposite effect.. So feedem sugar, molasses are my fave sugar source. Once you trigger flowering and leaves become a sugar source, you can stop feeding sugars via watering and continue via follar spray because the same process takes place in leaves at that time

Happy gardening

OregonMedGrower said:

Harvesting lights on/lights off is only a pleasure a personal grower can experience..when your a one man show chopping down multiple pounds of meds ,you have no choice..but personally I have never seen a noticeable difference in the quality of bud harvested lights on/off or sitting in the dark for a couple days

I would think the drying process would play a WAY bigger role in the finished product,but that's another thread in itself

lots of good thoughts in here

Click to expand...

I recently tested the idea of taking a plant just before lights on VS taking a Plant after 4 hours of lights on.
I was flowering 4 MasterKush plants under a 600 watt HPS.
I took 3 just before lights on and 1 like I usually would at the middle of the day.
All 4 were dried and cured exactly the same.
The plants taken at just before lights on were noticeably smoother.
The plant taken during lights on tasted just like every other Masterkush I flowered for the last couple of years.

The difference is on the tongue and the back of the throat, it was a large difference.
I associate the 1 plant with a harsh aftertaste, one that I was used to from the strain.

I thought the harshness was from the strain or from my lack of growing knowledge.

From now on I will harvest my plants just before lights on.
Bless,
DZ

I veg under 18/6, the only advantage I am sure of is starting my lights on at the same time in my veg and my flowering tent.
The plants are a acustomed to waking up at the same time rather than trying to get a plant used to a new light cycle like going from 24/7 to 12/12 which for me takes an extra week to 10 days.

So my plants start to flower faster with the same start time versus when I used to use 24/7 for veg and clones.

I though more was better but in the end the lights off helps with the circadian rhythm of the plant.
Just my .02
Bless,
DZ

Bangaman said:

I would like to clarify all the urban legends and old lady tales about 24/0 versus including some dark periods in your grow.

I will keep this simple because many come to these forums for guidance.

First off, For all beginners, the sole practical differences between 24/0 versus 18/6 are time and money. and if you are like me, time is money. I run 4 1000 watt lamps 2 in 2 8x 8 rooms and each increase my electric bill by $50. I do not run AC, but each lamp has its dedicated cooling fan and exhaust fan circuit. I run a humidifier hooked to the humidity port of the Environmental Controller in each room.

I journal each crop from seed to harvest. i measure height (growth rate) of each plant every 3 days(or watering) until i begin LST. There is on average 25% - 35% faster growth with 24/0 light than 18/6 depending on Sativa dominance or Indica dominance in the plant genetics. With 24/0, I shave my time to harvest by 25-30%. that is, i harvest 2-3 weeks quicker. Do the math and compare what you are really spending with the daily savings in 6 hours of darkness versus the savings at zero darkness. At 18/6 your overall electric bill is higher per crop. You spend more time on each crop (what do you consider your hourly wage?). And then there is the opportunity cost that comes with not having the product ready "in time"

Now for the science: on earth we have 3 major types of plants based on how they "cook" or "fix" Carbon(that means separate Carbon from CO2 and make sugar). They are C3 carbon fixation plants like Cannabis and C4 carbon fixation plants like corn, sugar cane and crab grass. Then there are Crassulacean Acid Metabolism (CAM) plants like cactus .

C3 fixation (C3 plants) thrive in areas where sunlight intensity is moderate, temperatures are moderate, carbon dioxide concentrations are moderate and groundwater is plentiful. The C3 plants can be considered Plant 1.0 compared to C4 plants. they (C3 plants) predate the C4 plants on the evolutionary scale. In dry areas, C3 plants shut their stomata to reduce water loss, but this stops CO2 from entering the leaves

Also we must clarify a common misconception in early academia (high school and freshman botany), that the ‘‘dark reactions’’ of the Calvin cycle (photosynthesis) actually occur in the dark. Truly it is called "dark reaction" because it takes place independent of the "immediate" presence of light energy. But because several enzymes in the so-called ‘‘dark reactions’’ are actually indirectly dependent on the presence of light for their activity, this "dark reaction" actually takes place 34/7 /365 regardless if it is a C3 or C4 plant and either plant does "feed continuously under uninterrupted light.

This is where c4 plants like sugar cane, corn and crab grass kick ass, they have evolved from c3 plants and have no limit to the intensity of light you throw at them. They simply keep pumping out sugars. Under dry hot conditions C3 plants shut their stomata to reduce water loss, this stops CO2 from entering the leaves to prevent photorespiration. But, this evolutionary advantage of c4 plants comes with an energy sink and that is why C3 plants will always outperform C4 plants if there is a lot of water and sun.

The sole purpose of a 12 hour dark time is to trigger flowering. The apparent growth or stretching you see is the plant using up resources (sugars) made during veg. during this phase the source for resources for other plant functions are reversed (leaves as source of sugars instead of roots) by the plant being in the dark for 12 hours.

NOW THIS IS WHERE MR / MRS SCIENCE TEACHER OR PROFESSOR "CALLED CANCER A DISEASE" instead of a condition because he/she did not know or thought students are not ready for the complex truth:

There is a third group of plants, the Crassulacean Acid Metabolism (CAM) plants, that survive in arid (dry) environments by opening their stomata only in the dark instead of the light, as do C3 and C4 plants. CAM plants only open Stomata at night to collection and fix CO2 in the dark. the stomata in the leaves remain shut during the day to reduce evapotranspiration. Examples are Aloe, Yucca(not to be confused with manihot/cassava), pineapple cactus etc.

by the way, several lab studies show that in cannabis;


The rate of photosynthesis and water use efficiency increased with light intensities at lower temperatures (20-25 °C)68-77F at 55% relative humidity and the maximum rate of photosynthesis in three university studies I came across was between 28-30 °C or 82.4 and 86F and under 1500 μmol of CO2 anything higher resulted in photorespiration (bad).

Nota Bene: In plants such as MJ, during the plant's growth period, usually during the spring or veg phase, storage organs such as the roots are sugar sources and leaves use up the sugars. After the growth period, when the meristems are dormant or when we induce flowering, the leaves become sources of sugar, and storage organs or roots become sinks. Developing seed-bearing organs (such as flowers) are always sinks. (this why it is critical to minimize leaf trimming once you induce flowering. It has not only been shown that via their roots, vascular plants actually absorb sucrose, glucose and fructose via processes of translocation, active transport, phloem loading and unloading. Cells in a sugar source or roots "load" a sieve-tube element by actively transporting solute molecules into it. This causes water to move into the sieve-tube element by osmosis, creating pressure that pushes the sap down the tube. In sugar sinks, cells actively transport solutes out of the sieve-tube elements, producing the exactly opposite effect.. So feedem sugar, molasses are my fave sugar source. Once you trigger flowering and leaves become a sugar source, you can stop feeding sugars via watering and continue via follar spray because the same process takes place in leaves at that time

Happy gardening

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Not sure if i read it right, but i assure you no one on this site would even consider harvesting their plants 3 weeks early. like week 6 on a 63 day day strain? I run 24 hours of light in veg and I've never experienced that.