Photoperiod Adjustment!

KBking · Jul 15, 2007

I'm sure many of you have read the GrowFAQ and seen the article on manipulating the photoperiod (amount of time the light is on or off). As we all know to induce flowering a plant needs approximately 12 hours of total darkness, but how long can we extend the daylight hours by using specialized timers, and when is it most effective? I myself am very interested in this matter as it would be extremely useful for people with smaller operations who want to get the most out of every bit of their space. So lets use this thread to collect information and hopefully bring together enough resources to allow people to get the most of of their plants. Anything from circuit diagrams for timers and where to buy 7 day timers to information on how photosynthesis changes depending where a plant is in its cycle should be posted here. Hopefully if we brainstorm enough people will be motivated to conduct actual side by side experimentation and give some solid results.

I'll start with this: it's a 7 day digital timer to allow longer "ON" light sessions.

Digital Timer Programmable 7 Day - Timers - Indoor & Outdoor

7-Day Digital Timer

And here is a link to an article discussing photoperiod manipulation

" I[SIZE=-2]N[/SIZE] [SIZE=-2]MANY[/SIZE] [SIZE=-2]FORAGE[/SIZE] [SIZE=-2]CROPS[/SIZE], including switchgrass, biomass yields are maximized in cultivars with a long growing period (Newell, 1968; Hopkins et al., 1995) or long leaf area duration (Madakadze et al., 1998a).
Variation between Alamo and Cave-in-Rock Switchgrass in Response to Photoperiod Extension -- Van Esbroeck et al. 43 (2): 639 -- Crop Science

Token · Jul 15, 2007

I've read something that sounds like something i read in high times not to long ago, something about 24hours on and 24hours off for flowering suposeble gives more time to make bigger buds but i think its a wast of time and takes longer to finish up a plant.

supergrow357 · Jul 16, 2007

if a plant takes 56 days to be ripe then it will also take just as many with that light cycle, but since your days are longer than a normal 12/12. it will take 56 x number of hrs. added to each day.if you only added 6 hrs. to each day you would have to wait a extra 28 days to harvest. perpetual harvest should keep the bud a coming.
i would like to see some side by sides for the photoperiod change.

beenthere donethat · Jul 16, 2007

Some growers out there are experimenting with using an 18 hour "day" rather than a 24 hour day. I believe Harvest Master has a controller out that allows this type of manipulation...

Like you, supergrow, I've yet to see solid side-by-side comparisons but I've heard that this does work.... beyond that I know no real details...

sticking to 12/12 here....for now

bt dt

kindprincess · Jul 16, 2007

14 hours is the shut off point. after 14 hours of light (if a continuous cycle) the plant will revert back to veg.

i've seen grows where people did 6 hours of light and 12 hours of dark. yeild was only slightly less than that of 12 12.

but, if you want the most out of your plants, do what is tried and true, the real standard of flowering (and for a reason). 12/12.

kp

gigi999 · Jul 16, 2007

I was tempted to try 6:45/12 as suggested by sk3tch3r.
The strain I am using has a very long flowering period, in theory I should be able to shorten it by giving it shorter photoperiods.
Does anybody have any experience doing this? would my yield be very different?

cheers

EmPot · Jul 16, 2007

gigi999 said:
I was tempted to try 6:45/12 as suggested by sk3tch3r.
The strain I am using has a very long flowering period, in theory I should be able to shorten it by giving it shorter photoperiods.
Does anybody have any experience doing this? would my yield be very different?

cheers

I am also interested in this.

dabull69 · Jul 16, 2007

i read something somewhere that said that if u go like 12 hours of light and like 8 or 6 hours of dark it will help. because the plant is most efficient durring dark period but it can only produce so much as its running on stored energy. so giving it a shorter dark period is essence is just like less time between battery charges. but i dont know how factual any of this is

KushMaster85 · Jul 16, 2007

But if you keep on charging a batter before it is due for a charge then it does not last as long. Just a thought! If the plant is like a battery.

Token · Jul 16, 2007

I never'd try'd the 24/24 and never will remember that its hormones that are activated by 12/12 that make the plant sex. Just because it's half and half doesn't mean anything the plant can only receive 18 of light a day.

potroast · Jul 17, 2007

Man O Man! I can't believe all of the stuff that some guys come up with. Not to single anyone out, there are a lot of speculations so far in this thread.

The plant is kept in flowering mode by giving her 12 hours of darkness. Giving her less than 12 hours of light will result in lower THC produced.

R. C. Clarke says in Marijuana Botany:

Marijuana Botany said:
Research has shown (Valle et al. 1978 ) that twice as much THC is produced under a 12-hour photoperiod than under a 10-hour photoperiod.

HTH

abudsmoker · Jul 17, 2007

you should have waited 10 more pages

krime13 · Jul 17, 2007

I have read on this site that less light douring veg is increasing your chances of females, till now I was doing 24/7, but next grow will probably be 18/6 or even 16/8, what do you think?

ferncakes · Jul 17, 2007

16/8 veg, 12/12 flower... thats just how it is guys, no other way. you can try out all the 14/10, 24/0 ideas and supposed secrets.. but ill tell u all the big growers use 18/6 veg and 12/12 flower and they're all millionaires, nuff said.

kindprincess · Jul 17, 2007

krime13 said:
I have read on this site that less light douring veg is increasing your chances of females, till now I was doing 24/7, but next grow will probably be 18/6 or even 16/8, what do you think?

actually, it was found that 24/0 light cycle produces more females. this was in greg green's cannabis grow bible.

ferncakes said:
16/8 veg, 12/12 flower... thats just how it is guys, no other way. you can try out all the 14/10, 24/0 ideas and supposed secrets.. but ill tell u all the big growers use 18/6 veg and 12/12 flower and they're all millionaires, nuff said.

the only difference i've seen between 18/6 and 24/0 is that constant light makes for bigger bushier plants. 18/6 is supposed to be less stressful (bs) and produce better root stock (bs). the only reason i can think that one would not veg for 24/0 is to conserve power.

kp

ferncakes · Jul 17, 2007

so thats ur opinion, you say bs to 1, and believe the other, altho both are just things you've heard/read, no facts.. im sure they both work.. which ones better? who's to say.. no one i know uses 24/0 so ill prolly never know 1st hand how effective it is, ill definitely never experiment with it, 18/6 works for me and everyone i know, so if it aint broke dont fix it

gigi999 · Jul 17, 2007

well I am not really sure about the 24/0. my 8 plants under 24/0 produced 7 males and 1 female. It might have been something else like temp or humidity but that was the result of 24/0 for me.

nongreenthumb · Jul 17, 2007

ferncakes said:
16/8 veg, 12/12 flower... thats just how it is guys, no other way. you can try out all the 14/10, 24/0 ideas and supposed secrets.. but ill tell u all the big growers use 18/6 veg and 12/12 flower and they're all millionaires, nuff said.

If you bother to read anything from someone with many years of experience, you may have read an article that was written by ed rosenthal, i personally would take anything ed says as fact when it comes to growing.

On 24/0 vs 18/6 he said.

The marijuana plant doesn't sleep or rest. If the plant is receiving light water nutrients co2 and all the other bits and pieces it needs it will grow, if you take one of these things away it stops growing.

If you run on an 18/6 schedule you are going to be losing 25% of your growth every day, some people say that its financial that they run on 18/6, his comment to this was that its false economy the plant will require the same amount of light to get to the same stage no matter what. So you have to give it the same amount of light to get to the desired flowering height, its taken you maybe a few days longer than it would have if you had used 24/0 multiply this over the space of a year or whatever and you will see that its costing you more money to run on 18/6.

I was never one for the 24/0 before i read this article and I havent even told you half of the information on it, but now I would always say to use 24/0 the only benefit of 18/6 is when the plant are going to be ready to flower too quickly and you want to slow the growth down.

ferncakes · Jul 17, 2007

nongreenthumb said:
If you bother to read anything from someone with many years of experience, you may have read an article that was written by ed rosenthal, i personally would take anything ed says as fact when it comes to growing.

On 24/0 vs 18/6 he said.

The marijuana plant doesn't sleep or rest. If the plant is receiving light water nutrients co2 and all the other bits and pieces it needs it will grow, if you take one of these things away it stops growing.

If you run on an 18/6 schedule you are going to be losing 25% of your growth every day, some people say that its financial that they run on 18/6, his comment to this was that its false economy the plant will require the same amount of light to get to the same stage no matter what. So you have to give it the same amount of light to get to the desired flowering height, its taken you maybe a few days longer than it would have if you had used 24/0 multiply this over the space of a year or whatever and you will see that its costing you more money to run on 18/6.

I was never one for the 24/0 before i read this article and I havent even told you half of the information on it, but now I would always say to use 24/0 the only benefit of 18/6 is when the plant are going to be ready to flower too quickly and you want to slow the growth down.

well i dunno who that guy is, but unless ive seen it for myself or my growing teachers tell me so, i have no reason to believe 24/0 is better than 18/6. BC grows the best pot in the world, and no one uses 24/0, they all use 18/6. and i am also in no position to start experimenting.. so for now, 18/6 it is

kindprincess · Jul 17, 2007

ferncakes said:
well i dunno who that guy is, but unless ive seen it for myself or my growing teachers tell me so, i have no reason to believe 24/0 is better than 18/6. BC grows the best pot in the world, and no one uses 24/0, they all use 18/6. and i am also in no position to start experimenting.. so for now, 18/6 it is

hahahaha!!! omg!! too funny!

ok babe, you got it then, please make a thread and teach us all how to grow it right!

kp

Photoperiod Adjustment!

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