36 Hour dark for transition?

Hey All,

I was at a hydro shop today and was talking to the guy about transition to flowering. He goes “you turned the lights out right?” And I said “uh what?- no”. And then he told me that you should turn you lights off for 36 hours before you switch to 12/12. He says it slightly stresses the plant into starting flowering faster.

Anybody ever heard of that?

@Majiktoker @Hogmaster @latewood @Aquaponic_Dumme @Donaldj @bob31 @Countryboyjvd1971 @dbrn32


I’ve read it on here @Ray4x. They say you give it darkness for 2 days before harvesting. It’s supposed to make the plant add a lot of tricomes right at the end. I haven’t done it though, still on my first grow. I presume the same kind of stress that splitting the plant a few days before would do. I have seen a few split the stem and give darkness simultaneousy as well.


I’ve heard that about harvesting. But he was saying between Veg and flower.

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Cannabis is a “short day/long night” plant, meaning it needs those conditions to bloom. The system cannabis uses to detect light changes is a group of receptors in the pigments of their leaves. There are 2 different receptors, each with a different task: Phytochrome Red and Phytochrome Far Red. They absorb light in different wavelengths and transmit that information to the plant.

Far-Red can be manipulated through the amount of light given to the plant. This receptor keeps the plant in the vegetative stage. Light in the far-red spectrum will signal this receptor to pass the chemical signal to veg. During times of light, both receptors are balanced in number, but in darkness, Far-Red receptors slowly change into Red receptors.

With longer dark periods, the number of Far-Red receptors reduces until there aren’t enough to counter the signal from the Red receptors, which tell the plant to flower.

Want to speed up your switch from veg to flower? Give plants an uninterrupted 24-36 hours of darkness before going to a 12-12 cycle. It will make more of the Far-Reds change into Reds, giving a more powerful signal to your plant that it is time to bloom. Normally, the transition can take a couple of weeks to be seen on your plants. By giving them a really long night, you can speed this up dramatically.


I I’ve heard all kinds of numbers thrown out there, as much as 48 hours. I haven’t done any more than 24 hours, and felt like that worked fine.

I don’t really think it’s designed to be a stressing mechanism, but to send a very clear signal to your plants.


@Ray4x I have heard all sort of stuff to concerning light schedules and I will not say I’m an expert on any of this and special schedules may work but I myself try to simulate as close as possible to natural light patterns? And in nature do the plants get a 36 dark period before they go into flower ?
With that said the only way to know if it works is to try it and record progress ?
I don’t think a plant switching into flower is stressful on them since it’s a natural progression of the plants life if your concerned about stressing it out do what nature does and step your times down a 1/2 hour every couple day until you hit the 12-12 mark
Happy growing all :cowboy_hat_face: :v: CB


I think you have to remember that this is a growing science (pun intended).

If I try something once, and it works, that is not science no matter how authoritative I sound in a plant store. If it works for you, great! But there may be 17 unmentioned factors that also make something work for that guy.

Or he’s never grown a plant and heard it from the last customer?


Oops, I missed that big detail, thanks @Ray4x

Actually yes I have , and yes I do , and yes I see a difference . Plants with a 48+ hour dark period as transition to flower start to produce faster and some what harder buds. I think I saw something about it on utube but not sure. Search advanced weed growing tips on utube might be there.



Awesome good to know.

I already flipped but something to keep in mind for next time!

I always love these questions. Once again we come to a theory. I
personally do not abide by this theory.

Without going into a lot of SOS on the topic; I will ask you; “Does the
Sun shut off for 36 or 48 hours in the middle of the grow season?” :wink:


It does on Monday!



Haha no!

That was my thinking too- but I also know that people have found ways to maximize indoor results going against what would normally occur in nature- so figured it was worth while to ask!


This statement @Ray4x!

It’s exactly what I think every time I see a “does it occur naturally” type of question or comment. Most of us don’t know what’s better, or we wouldn’t be asking. Outside of doing side by side grows with control methods we probably never will. But there are a lot of instances where replicating an outdoor grow doesn’t make sense for everyone.

Im not contradicting what others say. But looking beyond it for things that support said thoughts. In the emerald triangle they hit 18 hours of light, and this is also said to be one of the best growing climates. They also have daily Temps of 100+ degrees, but we don’t target that for our indoor grows. Nor does stem splitting happen naturally, but plenty of people seem to be having success doing it.


Regarding what occurs naturally, do any indoor growers “make it rain”? Do you “foliar feed” while the plants are in flower?

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Nope, not me anyway.

I started a question topic about this to get more input.


Just because the sun doesnt shut off for 36 hours doesnt mean it wont work or have a positive effect. If anything it may be something worth while to study yourself and see. Im definitely going to try it with some Bruce Banner seeds i got from ILGM.

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Yes my guy, yes!!!

Good choice on the seeds @Oscar7768, let us know how the light schedule goes.

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