[ShroomDr]

Most growers read 12/12 and assume plants need 12 hours of darkness, and this simply is not the case. 12/12 is a convenience. Some people grow 21:30 on / 12 off, (I think thats right. Its suppose to mimic 5 dark periods per 7 earth days) or 9:30 on / 12 off (9 dark periods). Both of these exploit the day period, im interested in the dark period.


At one time, I was growing 13 hours on, 11 off, thinking the extra hour of light would give the plants more energy (1/12 more). Now i am forced to flip flop this particular circuit. I have two tents with vertical cool tubes, each one on a timer set for 11:45 of HID lighting, to make sure both lighting systems wont be on at the same time.

Due to the vertical lighting, i am forced to do the garden maintenance when the lights are off. Rather than losing out on valuable photosynthesis time and falling back on my knowledge of 11 hours of darkness being perfectly acceptable, after the light goes out, i open the tent (basically right away).

Long story short, I have spent over 2 hours with the tent open (tent lights off, room lights on), giving them less than 11 hours of darkness countless times. Sometimes they get the full 12:15, sometimes its 11, sometimes its down to 10, without ill effect. Ive been doing this for 3-4 months, perpetually growing 6 strains, 7 phenos, no problems.


I probably wouldnt push it much further, but i'd love to know if others have. What's the shortest dark period needed to force and keep 99% of strains in flower? I want to say its close to 9 a little more.






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[VerdantGreen]

it would be strain dependent.

but also giving them a shorter night even every other day would be different to doing it every day, and the speed of flowering and ripening might change.

the best way to do it is sposed to be to retain the 12 hours dark but give a longer day of 14-16 hours. day length matters much less than night length to make them flower.

VG

[DocLeaf]

^^ wat VG said.

12hours.

[ShroomDr]

Originally Posted by VerdantGreen

it would be strain dependent.

but also giving them a shorter night even every other day would be different to doing it every day, and the speed of flowering and ripening might change.

the best way to do it is sposed to be to retain the 12 hours dark but give a longer day of 14-16 hours. day length matters much less than night length to make them flower.

VG

might and suppose are conjecture, im looking for hard evidence.

Originally Posted by DocLeaf

^^ wat VG said.

12hours.

ive already demonstrated you dont need 12 hours. 12 hours is incorrect.

[VerdantGreen]

indeed some strains will start to flower under more than 12 hours dark, but you missed my point - that its better to have a longer day of over 12 hours but keep the night period at 12 hours.

for shorter nights the only way to find out exactly what you could get away with would be to experiment with each indivdual pheno of each individual strain, good luck with that.

and as i said, you may be able to get it to start flowering in say 10 or 11 hours of darkness, but it may also make it take 2 weeks longer to ripen. sorry i cant give you 'hard evidence' im just trying to help by telling you what i know and what i think may happen, based on a reasonable knowledge of how auxins work and observing how plants grown outside will accelerate their flowering as the nights get progressively longer.

VG

[ShroomDr]

Originally Posted by VerdantGreen

indeed some strains will start to flower under more than 12 hours dark, but you missed my point

You have certainly missed my point, i have not mentioned 'more than 12 hours of dark'.

To the best of my knowledge, marijuana needs a certain amount of darkness to build up enough flower hormones. Most people think this is 12 hours, and it obviously is not. Its not 11 hours, based on my own indoor observations, and the shortened dark period has no effect on ripening time. (Ive been running a couple of my current phenos for years).

'observing how plants grown outside' is a very poor analogy IMHO. You can't control the dark period. It becomes 'the chicken or the egg' when attempting to correlated outdoor ripening and longer dark periods. Even the best example of an 8 week flowering plant vegged indoors under 24/0, and placed outdoors 8 weeks before vernal equinox would not be a good analogy, as the sun continues to build intensity as the earth tilts (something not happening indoors).

But i digress, Im not interested in longer dark periods, only the shortest possible dark period to build up the flowering hormones. Im not trying to get into an argument, just some useful discourse, as that is what is most helpful to all readers.

I want to know the least amount of dark period hours other users have used, and if they have pushed it too far.

[hempluvr]

Originally Posted by ShroomDr

You have certainly missed my point, i have not mentioned 'more than 12 hours of dark'.

To the best of my knowledge, marijuana needs a certain amount of darkness to build up enough flower hormones. Most people think this is 12 hours, and it obviously is not. Its not 11 hours, based on my own indoor observations, and the shortened dark period has no effect on ripening time. (Ive been running a couple of my current phenos for years).

'observing how plants grown outside' is a very poor analogy IMHO. You can't control the dark period. It becomes 'the chicken or the egg' when attempting to correlated outdoor ripening and longer dark periods. Even the best example of an 8 week flowering plant vegged indoors under 24/0, and placed outdoors 8 weeks before vernal equinox would not be a good analogy, as the sun continues to build intensity as the earth tilts (something not happening indoors).

But i digress, Im not interested in longer dark periods, only the shortest possible dark period to build up the flowering hormones. Im not trying to get into an argument, just some useful discourse, as that is what is most helpful to all readers.

VG answered it right. It is strain dependent. 12/12 is widely accepted because most all strains will flower indoors under 12hrs of darkness 12 hrs of light. However if 12 hr days were needed to flower then outdoor strains would not flower until late in the year. For instance White Widow will flower with 15 hrs of light and 9 hrs of darkness. With 12 hrs of light she finishes nicely but with 15 hrs of light she has more weight and better crystal production..IME!

At the same time. Some strains vegged under 24 hrs of light will start to flower if dropped to 18/6. Based on the fact the days have been very long and never ending so a cut to 18/6 or 17/7 may cause it to flower. After all the days are shorter. I had this exact thing happen with a bagseed sativa I had in 2008. I vegged for 24 hrs for 2 months then decided to cut back to 18/6 and everything in the veg room stayed in veg except the one plant which began to flower. Just my

I think u are right tho...9 hrs of darkness would work nicely with most 8-9 weekers!

[STUPPA]

I think the amount of dark needed to maintain flowering might be different to the amount needed to induce it .What i mean is it might require more dark time to start the flowering response than it would to maintain it in later flowering .
Plants might not start flowering with 9 hours of dark period but later in bloom 9 hours dark might be sufficient to maintain flowering, not saying it is tho LOL .

you would have to do a painstaking experiment involving gradually increasing the dark period a half hour at a time and then leaving it at that length for 2 weeks ,then if no flowering occured you would have to do it all over again. That still would'nt give you an accurate figure tho cos you have to take into account the gradual build up of flowering hormones and how long these hormones can remain active.

[zenoonez]

Clones + cfls + cheapo timers = win

[*mistress*]

around 8-9hrs.....

very simple:

reduce light by :30 min, every 48hrs....
from 24/0, to around 15/9.... 9hrs dark generally initiates reproductive organs....

though each specific cultivar will have its own unique flower/fruiting trigger, 9- 9 1/2 hrs dark generally triggers & maintains flowering.....