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Effects of different photoperiods on flowering.

C

Charybdis

Member
If you have a strain that flowers readily - say under 16 hours of light - would you be better off to switch to 12/12, or if it'll flower at 16 should you go with 16/8? It seems to me that if it'll flower with more light, you'd get more growth at 16 than 12. I know some growers run pure sats at 11/13 or even 10/14 instead of 12/12, but I think that's usually just to get them to actually flower.

Also, I don't remember where I read it but I remember hearing about a fairly new technique where you can run 12/6 - with a dark period half as long - and still get the same yield in reduced time. Is anyone here familiar with that? I couldn't find any threads on it.

Thanks.
 
Maj.PotHead

Maj.PotHead

End Cannibis Prohibition Now Realize Legalize !!
Mentor
Veteran
when you say flowering do you mean full on stacking cylx's {the flowers makn buds} or just preflowers at the internodes ???

as for amount of flowering time yes theres a few threads here about reduced flowering time but it also comes with reduced yields

i highly suggest 12 on 12 off lighting during flowering indoors.

now for veg theres a thread around here about lighting = yield

24 hrs on = yeld
20 on 4 off yield
18 on 6 off yield

conclusion seems to be 20 on 4 off for best rootmass for the end yield, personally i run 18/6
 
funkervogt

funkervogt

donut engineer
Veteran
Charybdis said:
I know some growers run pure sats at 11/13 or even 10/14 instead of 12/12, but I think that's usually just to get them to actually flower.
Click to expand...

Think about where these ladies are originating - the equator. At the equator the summers and winters basically have the same amount of light each day to the tune of about 12 hours. This is why they'll do 11/13 or 10/14 all the way through flower.

Charybdis said:
Also, I don't remember where I read it but I remember hearing about a fairly new technique where you can run 12/6 - with a dark period half as long - and still get the same yield in reduced time. Is anyone here familiar with that? I couldn't find any threads on it.
Click to expand...

I've heard variations of this VERY untested theory a few times on OG, but never here. I personally would not mess with the light schedule unless you have some solid scientific reasoning for doing so. If you have an extra room to play around with this, I say more power to you, but I definitely would not experiment with my girls by changing their concept of how long a day is :)
 
L

LJB

The point of altering the photoperiod is to create an artificial environment in which a more constant rate of photosynthesis is achieved. In other words, less peaks and valleys.

Once the sun comes up or the lights turn on, contrary to what you might assume, it's not as if the plants also instantly turn on to so to speak and than stay on for the entire time of exposure to light.

I know one grower / scientist with a working theory about 32 hour photoperiod.... That is 18 on, 14 off during bloom. He swears by it.

I have nothing else to add.
 
L

LJB

Who rated my posted as not being helpful and didn't bother to respond it?

The grower asked about using more than 12 hours of light during the bloom cycle.

I explained why people attempt do this which also explains why it might not work and also mentioned someone else's working theory.

What is anti-helpful about this? The title of the thread is " Effects of different photoperiods on flowering"...

edit: I see it was Maj.PotHead.

So what's the problem with the information that was posted? Explain your actions for the rest of us.
 
I

icmag.is.#1

If I were you I would just stick to the ole 12/12, especially for a sativa, from what I can remember most sat's come from equatorial regions which is damn near always on a natural 12/12 cycle.

And please explain this 12/6 theory for me.. Thats 12 hours on and 6 hours off and another 6 hours of not so light/dark? Or is this completely different from a 24 hour cycle?

Whoops... Guess i shoulda read funk's post before I repeated him
 
R

RustyShackelfor

New member
for a reduced flowering time, wouldnt it be the light cycle that was reduced 6/12 light/dark to achieve this?? and isnt it obvious that with a reduced light period the phosynthetic reactions reduced ie less yeild. this makes sense to me but i could be wrong
 
Andyo

Andyo

Active member
Veteran
Actually youll find that on the equator you get 11/13 12/12 13/11 im living 8 degs north of the equator and we get 10.5/13.5 12/12 13.5/11.5 and all hours in between obviously the times being the shortest day the equinox and the longest day respectivly .
 
B

Born420

seems like if you simply mimick the sun as best you can, that just seems to be the most logical approach. Now I am a newbie and claim no expertise whatsoever. But, the one thing that seems to ring true in everything I have learned is this. The plant needs what it needs for thousands of millenium. You can influence, but ain't nothing you can do to change that. The plants needs are the plants needs , period.
 
one Q

one Q

Quality
Veteran
IMO its a balance of Money/Power Consumed and Growing. 12/12 seems to do the best for most situations.

I remember OG and all the threads about 16/12 and how to set up the digital timer and what not. But I think the conclusion wasnt as good as the extra power used or someshit.

ps this post isnt helpful either just what I have to contribute...
 
ShroomDr

ShroomDr

CartoonHead
Veteran
First, my lights are on at least 12h15m and probably more like 12.5on/11.5 off.

ive read where people do 5 12hour dark periods per week (that's something like 21.5on/12off). You could also do 9 dark periods per week (i think its something like 8.5on/12 off.

The plants mature based on the # of dark periods.


i would assume there is a tipping point; I would love to see someone try something like 36on /12 off (3.5 dark periods per week)
 
Blckbrd

Blckbrd

Member
I flower using 7 on / 12 off. I veg at 24 hrs-on for up to a month to get the desired size, then use a cycle timer for the 7 / 12. Yeild has always been fantastic using 1000w. I suppose the theory is that they might get a little bigger (?) with a few more hours of sun a "day"/dark period.
 
H

Helis

Member
Blackbird have you always ran this time period? What sort of strains are you running? Aside from electricity, do you have any reasons to be running it like this?
Have you done comparison grows or have recorded yields vs 12/12?
Very interested in different light patterns, I know Dr. Bud talked about using a short day and a long night period with one day of full dark per week.
Interesting stuff...
 
Blckbrd

Blckbrd

Member
I have been running this time period for about 7 or 8 grows of White Widow, bubblegum, blueberry, and now doing LSD, Lemon Skunk, and Master Kush. ChemDog/SourDiesel is on deck, and I hope to have Tom Hill's Haze right there with them on the next venture.

I don't do it for electricity - committed to the best grows I can do, I am more than willing to pay the bill. Not trying to skimp anywhere. I have always used 1000w mh for veg (24/7 - no sleep period at all) and 1000w Hps for flower. It's a dual ballast so i just switch bulbs. Just tried a 1000w dual spectrum that I am runnning now for the first time. Switched it about 20 days into flowering - just trying something new. So far so good, though I don't see any real difference in the development.

I have never really accurately compared/weighed yeilds, but from careful observation over the many months of tending, I am convinced that there is no less weight in the shorter cycle. I veg the plants to the size I want - usually pretty big. Then I flower them on the 7/12 and the product is as good quality and weight-wise as when running the 12/12.

I really do it to just speed up the harvest time. I like genetics that take 70+ days to flower and the 7/12 cycle is about 24% less time ( over two weeks less ) of flowering time. The finished product is huge, dense, and true to the genetic expectation. I have not observed any detriment at all. I suppose a theory could be that with more light energy, the flowers could be bigger, but that's hard to believe. I typically have to tie them to the ceiling to keep the bud-laden branches from breaking or tipping the resevoirs.

All in all, having grown both 12/12 and 7/12 exactly the same otherwise, it is my impression that 7/12 saves time without compromising anything. The plant is "tricked" into shorter day/night cycles.

I can't recall where the heck I was informed that 7 hrs is really as short as you should go, but it is a notion I have adhered to.
 
J

JewBilly

New member
7/12 cycle

7/12 cycle

Hi Blckbrd.

I'm interested in learning more about this 7/12 flowering cycle you use. You can contact me directly by message or email you want. I'm thinking about doing it, but I have also read that 12 hours of light and 6 hour of dark will work (See uphill post at http://forum.grasscity.com/advanced...8-do-vegging-plants-need-any-dark-time-2.html) I get it about the 20-25% increase in production. I'd like to know how many watts/ m2, and the strains and nutrients you are using.

Thanks for posting your interesting experience.

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Blckbrd said:
I flower using 7 on / 12 off. I veg at 24 hrs-on for up to a month to get the desired size, then use a cycle timer for the 7 / 12. Yeild has always been fantastic using 1000w. I suppose the theory is that they might get a little bigger (?) with a few more hours of sun a "day"/dark period.
Click to expand...
 
Blckbrd

Blckbrd

Member
JewBilly said:
Hi Blckbrd.

I'm interested in learning more about this 7/12 flowering cycle you use. You can contact me directly by message or email you want. I'm thinking about doing it, but I have also read that 12 hours of light and 6 hour of dark will work (See uphill post at http://forum.grasscity.com/advanced...8-do-vegging-plants-need-any-dark-time-2.html) I get it about the 20-25% increase in production. I'd like to know how many watts/ m2, and the strains and nutrients you are using.

Thanks for posting your interesting experience.

@@@@@@@@@@@@@@@@@@@@@@@@
Click to expand...

Sorry for the delay .. just found this thread again. 12-on and 7-off seems like another way to speed up the 12/12 cycle. Might be useful for those sativa/haze strains. I do a 24 hr on vegetative & have never tried shortening the night cycle. I'd be inclined to do something less than 12 on, however, to ensure triggering the plant's flowering.

I use GH flora series under 1000 watts/4x4'. Always very happy, barring the invasion of some effing virus that I am now battling.
 
S

secondtry

Charybdis said:
If you have a strain that flowers readily - say under 16 hours of light - would you be better off to switch to 12/12, or if it'll flower at 16 should you go with 16/8? It seems to me that if it'll flower with more light, you'd get more growth at 16 than 12. I know some growers run pure sats at 11/13 or even 10/14 instead of 12/12, but I think that's usually just to get them to actually flower.

Also, I don't remember where I read it but I remember hearing about a fairly new technique where you can run 12/6 - with a dark period half as long - and still get the same yield in reduced time. Is anyone here familiar with that? I couldn't find any threads on it.

Thanks.
Click to expand...



Cannabis is a 'long night' plant, so it needs 10-12 hours of darkness to flower, the hours of light doesn't effect flowering, that's the job of darkness. That said, you could change the diurnal hours (length of one day) from 24 hours to 28 hours, that is what I do. I use 16/12 for flowering. For pre-flower I use 8 on/12 off; that limits stretching and helps keep internodes close, it also reduces the pre-flower time from say 14 days to 10-12 days. 8 hours is about as little daylength as is wise.

For veg I use 16/8. It's best to not exceed 16-17 hours of light a day, 18 hours can be too much in terms of reducing Pn (rate of photosynthesis), carbon assimilation and partition, etc. Running lights at 24/0 will make the Pn drop drastically after the first two-three days or so.
 
S

secondtry

The info about 6 hours of darkness has to do with far-red lighting and Pf/Pfr (ie. phytochrome). It's not proven for cannabis and IMO is not worth pursuing at all, 12-14 hours of darkness per night is good.
 
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