Question for everyone to chime in on

Got a question, everyone give their input!! What part of the 12/12 cycle makes plant start budding? Light or dark? Would it be possible to give 12 hrs of dark and still maintain 18hrs of light and it still flower? Would have to manually switch lights but just a thought that came to my mind

The length of darkness is what triggers flower as far as I know. Going over a 24-hour cycle seems unnatural and would also mean your feeding times, etc would constantly be changing, if that makes sense. Seems like it might be more trouble than it’s worth.


Was just thinking if I can continue on with vegetative growth while also flowering it may keep producing, probably over thinking :thought_balloon: :joy::+1::thinking:

It is a hormone process in the plants. At different stages of growth plants will have different hormones for different things. When 12/12 is triggered it triggers a certain hormone in the plant letting it know it is sexually mature and able to produce @Dankgrower88 hope this helps, and hope it clears things up a little for you @Matthew420, and if im not mistaken these hormones have certain names just dont know the names right off hand and for some of us its not what we think its what we know


I really don’t know. I’m curious what people think as well. Just seems out of whack somehow. But so did lots of other things that turned out to be great.


So if I was to give complete 12 hours darkness but kept lights on for 18 what would happen? Stay in veg? Or stress it out?

Hermies for sure I bet.

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Kinda what I was thinkin too

Well so to speak there are 24 hours a day so what are you asking, if you had it on 12 hours of darkness (when in flower or not in flower) and went to 18 hours would it hermie? Well that depends on if it has already begun flowering. If she has started producing white pistols chances are yes you will risk turning your plant into a hermie.

If your in veg and lights have been on for 18 hours and you went to 12 hours of straight darkness, than would it hermie. No it couldn’t, most you would see if the plant was mature enough is flowering triggered over night

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I read in Ed Rosenthals marijuana book, that some growers use 12 hours of light, and 12 hours of blue light and that will make the plants grow vegetatively still, but they semi flower and show sex as well.



Hope this helps

To start your plant flowering when growing indoors, you need to mimic the lighting conditions found in Fall/Winter. This means taking the plant from the 18/6 marijuana light cycle used in the vegetative growth stage, and changing it to 12 hours light/ 12 hours darkness. You will also need to reduce the number of lumens you are giving your plant. This means changing your bulbs from a summer sun replicating 6500k, to 2700k which mimics the warm red sun of fall. As marijuana is a fall flowering plant, the shorter light hours and red light reproduce the conditions in nature. Be careful not to make this change before the plant has shown its pre-flowers as this will stress the plant and may cause it to become a hermaphrodite.
Marijuana Light cycles


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The name of the hormone you seeking for is florigen @Majiktoker :wink::grinning::+1::innocent::v:

i’ve kept mine on an 18/6 until they flowered, now my schedule 14/10… why 14/10 you ask? well i have autos and have heard that 18/6 would work for them,so i went out on a limb and try to keep them at 14/10…thats 14 light 10 dark… there is my five cents worth, right or wrong!lol

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Pr and Pfr?

"Flowering in response to day vs night hours is called photoperiodism and it is the most significant influence on flowering.
Short day is actually a misnomer, as I thought I made clear above, it is the length of the night that has the effect on the plant’s biology. These plants should actually be called “long night” plants.
I somewhat inaccurately called them hormones, I used the term loosely more so as it is something a lot of people can understand on kind of how the biology works.
More accurately they are called phytochromes. Plants make 5 of them: PhyA, PhyB, and also C, D, and E.
The mechanism of photoperiodism in short-day plants is known as the ‘hourglass model’.
Phytochromes come in two varieties that are interconvertible. One absorbs red light (around 660 nm). The other absorbs far-red light (around 730 nm).
We can express these as Pr and Pfr, abbreviated for ‘phytochrome red’ and ‘phytochrome far-red’.

Absorption of red light by Pr converts it into Pfr. And vice/versa, absorption of far-red light by Pfr converts it into Pr.
In the dark, Pfr spontaneously and gradually converts back to Pr.
So the plant pretty much needs the full uninterrupted dark cycle (8-13 hours depending on strain) to convert all the Pfr back to Pr. and to carry out the supplementary reactions leading to the release of the flowering signal (“florigen”).
This is why “The Gas Lantern Routine” works and prevents the plant from going into flower. Only a flash of intense 660-nm light and the Pr is immediately converted to Pfr, undoing all the night’s work.
There are ways to use far-red to boost or speed up flowering, but I’ve already gone into more detail than I’d like, as some of this might be hard to understand or too much to read through, hence why I normally just keep it simple and say “hormones”, lol.
Happy growing,


Thanks @Niala

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You’re welcome :innocent: :v:

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