# Shortening photoperiod during flower?



## teddy d (Apr 2, 2011)

_a bunch of random photoperiod questions that have been on my mind. Im sorry if it is stupid or does not make sense._
I was wondering if it would make a difference in yield if you started flowering with 24 hours of darkness to trigger flowering. then set the lights at something like 13on/11off for the first week or two, then go to 12/12 for a couple weeks, then go to 11/13, and then 10/14 the last week or 2. and finished with 48 hours of dark before harvest.

It makes sense to me that shortening the light would make the plant "try" harder to get pollinated  as it would detect  the shortening of days....

but, does that matter at all? It almost seems as though the plant just has a switch for budding and once you flip the switch its going to flower normally no matter what.

actually when I think about it, it seems like it would be better to start with 11/13 to trigger flowering and then  give the plants as much light as possible without reveging them. (more light durring flower = bigger yield?)

*can you switch to 12/12 for a week to trigger flowering and then switch to 13/11 or even 14/10 to maximize the hours of photosynthesis and create larger yields without revegging? * how flexible is the flowering photoperiod?

( I know it is strain dependant because certain strains need short days to flower) but i had an outdoor plant that was flowering with 14.5 hour days so why not give a strain like that 14 hours of light to increase growth....?


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## niteshft (Apr 2, 2011)

The plant isn't alive in the sense that it "detects" anything. Marijuana produces an hormone that induces flowering ALL the time but light destroys it. The shortening of the days enables the hormonesto build up to a point where it triggers the the plant to flower. I think some plants produce more hormones than others and therefore can get by with a somewhat shorter dark period but you would have to experiment to see if what you are growing is one of those.

EDIT: Studies have shown that 12/12 is the best for bud production on average.


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## BBFan (Apr 2, 2011)

:yeahthat: :goodposting: 

You are correct Teddy d- More light does equal more bud.  That's basic science.  I usually run 13/11 and I know my yields have increased but I have never done side by side testing to measure the difference.

I would certainly never go less than 12/12 though as that HAS been proven that a signficantly less amount of thc is produced (I don't remember the percentage, but it is in Clarke's book) I believe the study was on 12/12 vs 10/14.

As far as triggering flowering by introducing an extended dark at the onset of flowering- I've never done it, I've never seen any studies done on it- all I've ever heard is anecdotal experiences.  Some people swear by it but can't produce any evidence to back it up.  Personally I think it's a myth.

Some things you just can't rush.


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## umbra (Apr 2, 2011)

there are 2 breeders that I know of who have been talking about this. DJ Short in his book, Cultivating Exceptional Cannabis, suggests something similar. As does Sonic, from Sonic seeds. I believe that their consensus was 13/11 for indicas and 11/13 for sativas.


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## PencilHead (Apr 2, 2011)

There's an old light-manipulation study floating around--can't remember who, where or what this early in the AM (but I will later)--that pushed the lights-on period to like 21 hours then complimented it with so-many hours of dark.

If I can find it, I'll link up.  Personally, I think it's **, like a lot of that old archived junk.


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## Locked (Apr 2, 2011)

A study in 1978 showed that twice as much thc is produced with a 12 hour photoperiod then with a 10 hour photoperiod....that is in the book Marijuana Botany by Clarke... I run 12-12 I don't get freaky with the flower period.


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## BBFan (Apr 2, 2011)

umbra said:
			
		

> there are 2 breeders that I know of who have been talking about this. DJ Short in his book, Cultivating Exceptional Cannabis, suggests something similar. As does Sonic, from Sonic seeds. I believe that their consensus was 13/11 for indicas and *11/13 for sativas*.


 
Doesn't that contradict the life cycles of equatorial sativas?


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## niteshft (Apr 2, 2011)

BBFan corrected me in a PM when I stated that the plants produce enzymes that trigger the plant to flower and is actually hormones. 
Thanks BBFan! :ciao:


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## teddy d (Apr 2, 2011)

why do i have to ask the odd ball questions that raise debate and folkore? haha


			
				BBFan said:
			
		

> :yeahthat: :goodposting:
> 
> You are correct Teddy d- More light does equal more bud.  That's basic science.  I usually run 13/11 and I know my yields have increased but I have never done side by side testing to measure the difference.





			
				BBFan said:
			
		

> I would certainly never go less than 12/12 though as that HAS been proven that a signficantly less amount of thc is produced (I don't remember the percentage, but it is in Clarke's book) I believe the study was on 12/12 vs 10/14.



so far *BBFan* is the only one who replied who has personal experience (with success apparently) using a flower period other than 12/12? I would love to read some of those studies if they are legit and anyone can find something worth reading.

*BBFan*What do you think about using a 14/10? even if longer days makes more bud Im wondering if the longer days will extend the overall flower period... plus you need to determine if the strain can flower with 14 hours of light. 

I would say start with 12/12 and then go 13/11 then 14/10? but you might be riding on the edge of reveg, so if one was going to try 14/10 it might be best to do so from the start since increasing the hours of light during budding might cause the plant to revert.

not sure whats better:
12/12 fist and then increase light
or
14/10 right off the bat

thanks for all the responses everyone, more opinions please!!
and studies if you can find them.


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## BBFan (Apr 3, 2011)

I only grow 2 strains that I've been growing indoors since 2008 and grew outdoors before that (finally gonna get new seeds this year :hubba: ).  But outdoors they would flower before we got to 12 hours of daylight so it made sense that they would also flower indoors with a similar schedule.

My opinion is to go straight to the new light schedule, but only if you're sure what the right schedule is.  If going to 14/0 doesn't induce flowering for the strain you're growing, you'll be losing a lot of time waiting for flowering that may not happen.

I found the right schedule for the strains I grow when I did an experiment on controlling stretch where I went from 24/0 to 13/11 over a period of a few weeks.

I'm sure 13/11 would work for most indicas, but I don't know about 14/0.  Good luck with it!


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## Mutt (Apr 3, 2011)

BBFan said:
			
		

> Doesn't that contradict the life cycles of equatorial sativas?



11 on 13 off does not contradict equatorials. 
Sometimes it's needed to get them to finish.


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## The Hemp Goddess (Apr 3, 2011)

Mutt said:
			
		

> 11 on 13 off does not contradict equatorials.
> Sometimes it's needed to get them to finish.



Actually, I think they are talking about the other way around--13 on and 11 off or 14 on and 10 off?


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