# 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


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## 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.


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## 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.


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## 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


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## 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


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## 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


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## 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.


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## 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


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## 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.


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## 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.


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## 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


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## abudsmoker (Jul 17, 2007)

you should have waited 10 more pages


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## 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?


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## 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.


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## 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


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## 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


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## 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.


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## 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.


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## 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.
> 
> ...


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


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## 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


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## ferncakes (Jul 17, 2007)

kindprincess said:


> hahahaha!!! omg!! too funny!
> 
> ok babe, you got it then, please make a thread and teach us all how to grow it right!
> 
> kp


show me a pic of your grow room, and ill show you one of mine.. we'll let the forum decide who's is more impressive.. we'll call it 24/0 vs. 18/6


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## nongreenthumb (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


He's the guy that taught your teachers. You need to stop being so stuck up your own ass right now, you seem to be playing a game, how to win friends and influence people.


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## kindprincess (Jul 17, 2007)

i won't deny that it's a pretty tent you're working with, it has much more of a visual apeal than my basement. but, nug for nug.... i'm sure we are par.

now, LISTEN to some other posts. 18/6 works, 24/0 works, anything more than 14 hours of light will keep a plant in veg. just because YOU like your system doesn't mean it's for me, or anyone else for that matter. 

i'll say this, what a waste! your bulbs are hanging the wrong way for optimum light, no reflectors.... you must love your power company, they sure love you!

kp


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## ferncakes (Jul 17, 2007)

kindprincess said:


> i won't deny that it's a pretty tent you're working with, it has much more of a visual apeal than my basement. but, nug for nug.... i'm sure we are par.
> 
> now, LISTEN to some other posts. 18/6 works, 24/0 works, anything more than 14 hours of light will keep a plant in veg. just because YOU like your system doesn't mean it's for me, or anyone else for that matter.
> 
> ...


old setup i had a few years ago, very low ceiling, just put poly on the ceiling no need for shades, got 2lbs/light twice in that room out of 4 times using CO2.. last 2 crops in that room got 1.25 lbs per light without CO2.. will have pics of new srtup in a day or 2


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## kindprincess (Jul 17, 2007)

ferncakes said:


> old setup i had a few years ago, very low ceiling, just put poly on the ceiling no need for shades, got 2lbs/light twice in that room out of 4 times using CO2.. last 2 crops in that room got 1.25 lbs per light without CO2.. will have pics of new srtup in a day or 2


sounds great, start a thread, i'd love to watch your sog.

kp


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## kindprincess (Jul 17, 2007)

sea of green, a technique based on many plants in a bed or table, just like you have in your tent. pm me if you'd like to chat, i feel bad having hijacked this thread for almost a page now....

kp


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## beenthere donethat (Jul 17, 2007)

kp..

In larger grows or in "tree" grows it isn't uncommon for folks to ditch their hoods and hang their lamps bare/vertical. If you've ever tipped a light up like this you''ll see how much light it radiates out to the sides rather than down... believe it or not..such lighting does have purpose. Ask "Krusty" (grew the largest buds I've ever seen with DWC/vert lamps) LOL.

I about spit out my coffeee on the "whos' Ed" comment. Geez...someone has been livin in a cave...

24/0 all the way here...have done so for over 15 years w/ great results. Anything less is wastin time.... like dropping your photoperiod an hour at a time rather than hammering down the 12/12. Yes..it will work...NO it isn't the fastest way or any BETTER and NO 18/6 doesn't "reset" the plant as some noobs believe. Man..where DOES this shit come from?

It's good for a laugh though...ya know?


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## kindprincess (Jul 17, 2007)

of course i do!

but, in his pic, i notice those arent' trees, but smallish plants... i would think there would be a better, more efficient way of lighting them....

but i know what you mean, i'm using a 400w hps for side lighting right now 

kp


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## nongreenthumb (Jul 17, 2007)

ferncakes said:


> whats sog?


roflmao, grows the best weed in the world, knows all the shit, but doesnt know what a sog is, c'mon even most newbs would know the answer to that.


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## [email protected] (Jul 17, 2007)

https://www.rollitup.org/indoor-growing/10050-some-stoner-set-timer.html hey token where did you get that tidbit about only being able to absorb 18 hrs,


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## ferncakes (Jul 17, 2007)

nongreenthumb said:


> roflmao, grows the best weed in the world, knows all the shit, but doesnt know what a sog is, c'mon even most newbs would know the answer to that.


sorry i dont use your lame american internet weed abbreviations and sayings lol


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## nongreenthumb (Jul 17, 2007)

ferncakes said:


> sorry i dont use your lame american internet weed abbreviations and sayings lol


Its not an american saying and I'm not american, its a standard grow term used the world over. Anyone who has planted a seed should have heard of it if not, then they must be too newbie.

But its good that your sorry for something, next you could try a sorry for all the attitude you been giving.


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## ferncakes (Jul 17, 2007)

nongreenthumb said:


> Its not an american saying and I'm not american, its a standard grow term used the world over. Anyone who has planted a seed should have heard of it if not, then they must be too newbie.
> 
> But its good that your sorry for something, next you could try a sorry for all the attitude you been giving.


lol sorry, some of this shit just boggles my mind tho, and goes against everything i have learned


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## nongreenthumb (Jul 17, 2007)

ferncakes said:


> lol sorry, some of this shit just boggles my mind tho, and goes against everything i have learned


Just because you learned it a certain way doesnt make other ways wrong, seriously though 24/0 does provide quicker growth than 18/6, the stuff about changing sex i dont believe for a second but for increasing the rate of growth 24 is better.


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## supergrow357 (Jul 17, 2007)

how much bud can you grow in a hr.. well with setup A 12/12 and setup B 22/12 being exactly the same conditions. it means that both setups would produce the same amount of bud every hr.
the only way i think this theory could work. would be if you can prove that certain weeks in the bloom cycle had a higher percentage of growth than the other weeks in the same exact conditions. if that were true than it would be worth it to extend that higher growth rate week of the cycle.


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## Token (Jul 17, 2007)

I'm not against 24/0 for veg all I'm trying to state is 24/24 isn't going to do any better then 12/12 and might not even work, you can't change millions of years bioengineering. Also I've read in high times that a reason for 18/6 is it per flowers faster then 24/0 due to the dark period.


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## [email protected] (Jul 17, 2007)

the theory behind it is...increasing day length = more stored energy .... more energy = more growth, plants dont have weeks when they grow, they grow at nite using energy from that day, that is what I have observed from my personal experience, i'm just a stoner not a plant physiologist, and you guys take it easy on the poor canidiot, he is still dealing with losing lord stanleys cup.


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## kindprincess (Jul 17, 2007)

[email protected] said:


> the theory behind it is...increasing day length = more stored energy .... more energy = more growth, plants dont have weeks when they grow, they grow at nite using energy from that day, that is what I have observed from my personal experience, i'm just a stoner not a plant physiologist, and you guys take it easy on the poor canidiot, he is still dealing with losing lord stanleys cup.


lol, i'm sorry babe, but the curing on the line thing was funny  

i'd like to add that i watched a thread of someone who flowered on 6.75/12. 6 hours 45 mins on, 12 off. his yeild was hardly affected.

kp


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## Token (Jul 17, 2007)

what would make someone only have the lights on for 6 hours 45min and 12 off, did he think it would finish up faster seen the days for the plant were speed up?


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## SmokerE (Jul 17, 2007)

I never heard of NGT or this guy....ed rosenbutts or something....super bud....sensi what?


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## [email protected] (Jul 18, 2007)

yep, fishing line in a dark garage, its low tech but when you have a lot of it to dry it is time saving


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## KBking (Jul 18, 2007)

alright, it's nice to see some people put up those links where their was actual info, but you'll gotta chill and not attack each other. As 707 said, the point is that supposedly the plant receives more light at once which allows it to create more ATP and complex carbs and other chemicals which helps it build and generate more cells, the only information I was basing this off was if you've ever heard about Alaskan fruits and vegetables, they're fucking HUGE, and i think that has to do (to a degree) with the fact that they have longer light periods. I was so interested in this information, because I have to grow from feminized seeds every time due to extremely tight space requirements, so I don't mind putting in extra time during the flowering phase if the weight and potency and increases even less than proportionally because either way I have to go through the same amount of veg time each run. But it's also very useful to know that less than 12 hours will produce at least somewhat comparable yields, because if your growing a sativa that takes 14 or 16 weeks to flower being able to chop it down to like 9-10 could speed up the turnover by a lot.


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## nongreenthumb (Jul 18, 2007)

Here is the end to this arguement finally. I have hunted it down and found the ed rosenthal article i was looking for. This should dispel all those stupid myths.

Its pdf format, but if you click on pages on the left and then scroll down to get page 60, its an ask ed column.
http://www.softsecrets.nl/_public/SSUK2007-03.pdf
Happy learning ppl.


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## supergrow357 (Jul 18, 2007)

NGT, that artical only talks about the 24 hrs. being better than the 18 hrs. of light during veg. it said nothing about having a day longer than 24 hrs. i still think that increasing your day (light hrs.) hrs. to 22 or 25 hrs. of light or whatever is still not worth it because your just waiting longer. of course you get more bud, but at the cost of more TIME.
I haven't done a lot of research latly on it compared to in 2000 -2001 i did a whole lot of research. I didnt find any then and still havent heard of any now.


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## nongreenthumb (Jul 18, 2007)

supergrow357 said:


> NGT, that artical only talks about the 24 hrs. being better than the 18 hrs. of light during veg. it said nothing about having a day longer than 24 hrs. i still think that increasing your day (light hrs.) hrs. to 22 or 25 hrs. of light or whatever is still not worth it because your just waiting longer. of course you get more bud, but at the cost of more TIME.
> I haven't done a lot of research latly on it compared to in 2000 -2001 i did a whole lot of research. I didnt find any then and still havent heard of any now.


I'm sorry but theres only 24 hours of light in a day, so if you run for 24 a day, then the light is constantly on, there is no dark period. As stated in that article the plant grows when it is photosynthesizing so if its on 24/7 then its getting maximum growth.

The same thing applies to flowering. You can only flower for a maximum of 14 hours per 24 hour cycle. The lights go on and off at the same time every day and you get the maximum results.

How does dong 24/0 instead of 18/6 cost you time?

18/6 is more costly on all fronts in comparison.


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## supergrow357 (Jul 18, 2007)

NGT, maybe you misunderstood me. I agree that 24hrs a day gives morew growth during the veg. state. day = 24hrs.
I'm talking about making a day = 34 hrs. every day in the bloom state. 22 hrs. on & 12 hrs. off. every day will get its 12 hrs. of dark. this will keep it in bloom. people say you get more, but i say you do at the cost of time. i hope im making some sense.


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## nongreenthumb (Jul 18, 2007)

supergrow357 said:


> NGT, maybe you misunderstood me. I agree that 24hrs a day gives morew growth during the veg. state. day = 24hrs.
> I'm talking about making a day = 34 hrs. every day in the bloom state. 22 hrs. on & 12 hrs. off. every day will get its 12 hrs. of dark. this will keep it in bloom. people say you get more, but i say you do at the cost of time. i hope im making some sense.


well i never agreed in the first place that this was a sensible way to go, it didnt occur to me this is what you were thinking because it seems crazy. You extend your flowering period just by having 14 instead of 12.


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## brown thumb (Dec 5, 2007)

thread dead ?



supergrow357 said:


> NGT, maybe you misunderstood me. I agree that 24hrs a day gives morew growth during the veg. state. day = 24hrs.
> I'm talking about making a day = 34 hrs. every day in the bloom state. 22 hrs. on & 12 hrs. off. every day will get its 12 hrs. of dark. this will keep it in bloom. people say you get more, but i say you do at the cost of time. i hope im making some sense.


there are several references around addressing this flowering photoperiod length (same source ?)
How do I manipulate the photoperiod for larger yields on Planet Ito?

I'm going to give it a try, junked 5 electric timers and got two 7 day digital timers for the lighting and ebb & flow controllers
- the digital timers also permit a much shorter flood period, but the large # of weekly events (70 max on/off feed cycles) makes finding a suitable timer difficult (tempted to use a PLC controller)


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## Nuggettree2 (Feb 28, 2008)

you guys know if changing the photoperiod from 18/6 to 24/0 is ok for the plant


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## eMotiv (Feb 29, 2008)

Nug, are you serious? Read the frickin thread!


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