"Crazy idea. . .anyone try less than 24 hour days for growing?

Hear me out.

Most growers use 12 hours light/12 hours dark daily cycles for flowering.

I can tell you from personal experience, plus common sense that many strains of cannabis plants don't really need 12 full hours of darkness to flower.

For example, in the Northern hemisphere, the autumnal equinox. . .the time when day and night are equally divided into 12 hour periods. . .generally occurs on September 22nd.

Anyone who has done an outdoor grow knows that by the third week of September, not only are most strains already well into flowering, but they're actually nearly finished usually needing only another 1-3 weeks to finish up. Typically, outdoor plants actually start flowering in August, when the days are closer to 15 hours light and 9 hours of darkness.

So here's the question. Let's say instead of flowering in 12 hours light/ 12 hours dark, I were to create artificial days with 12 hours of light and 9 hours of darkness. . .in effect shaving off three hours per day of dark time.

Obviously, physically going about this poses some challenges. Ordinary cheap timers work on 24 hour-day cycles, as do most normal human schedules. Running 21 hour days would mean that the light cycles would shift three hours earlier every day. But lets say for arguments sake that I rigged a custom timer and didn't care about the shifting light cycles.

In theory now, I would be giving flowering plants the exact same amount of light (12 hours per day) as most growers do. By shaving off 1/8 of the total day length, I should be able to give the plants the same amount of total light as a typical flowering cycle, and the same amount of total days, but in only 7/8ths the time.

This could shave a full week off the typical 8 week flowering cycle down to 7 weeks, or a 10 week cycle down to just under 9 weeks.

Now realistically, I don't think an extra week is going to make any difference to the casual grower. and the hassle of moving light periods would probably outweigh the benefits. But to a professional grower, reducing crop time by 1/8 could effectively boost output by 12.5%. That's a pretty significant amount. . . .if a commercial grower had some magic nutrient formula that would boost their output by 12.5% they'd grab it in a heartbeat.

So. . .anyone actually seen this attempted?

Any thoughts?

ive seen people attempt similar photoperiod tests from bros and none seemed to produce more or save money on energy. maybe with some heavy indicas. I say you go for it and rock a journal with a few different beans

I agree with cacamal; we volunteer you to do this experiment.

Again, for a given harvest, since the total time your lights are would be the same for say 70 cycles of 12-12 vs 70 cycles of 12-9, you wouldn't expect to save any energy this way. By design you're using the exact same amount of light-hours, so your total energy cost PER PLANT should be the same. For the same reason, you also wouldn't expect to get any more yield out of a given plant or a given harvest.

In fact, since at 12-9 you'd be running more hours of light per calendar month, you would see a corresponding 12.5% INCREASE in your monthly energy bill if you were running a perpetual setup.

Put more simply, the plants should end up exactly the same under 12-12 or 12-9, just in 12-9 they should finish a week sooner. The only point of the exercise is to finish the SAME grow in less time. If you are growing consecutive harvests, or even a "perpetual" harvest setup, you should be able to boost your yield by 12.5% *per unit time*. In other words, by squeezing a "day" into 21 hours, you might be able to get 6 harvests in a year, instead of 5.

As to doing the experiment, there is no way I could personally do it in any way that would get meaningful results.

Its not a trivial thing to do. The best way to do this would be for someone who has an established history growing a certain strain repeatedly under a given setup, to the point where they have a fairly consistent output and they know a. exactly how long in days it takes for their strain/crop to mature, and b. exactly how much yield they can expect. At that point, they could try running 12-9 to see if the plants actually did finish faster, and how the yields compared.

For a small amateur grower, one or two grows comparing 12-12 to 12-9 even under otherwise identical conditions really wouldn't prove much, since I think most non-pro growers would experience more than 10% variability in harvest weight under normal circumstances even using the same strain.

At best, a small grower could try 12-9 using an established strain and just see if, indeed the plants did finish a week faster that way. But again, since plants can ordinarily vary in harvest time by a week, you'd need otherwise identical parallel grows using clones to prove that the 21 hour days shaved off a week.

We're not asking you to do a control group with comparative data, just do a casual test to see if it works, a proof of concept. Personally I think there are easier, better, more natural ways to increase yield, but this is interesting and I would love to know how it turns out.

They make timer that doesn't operate on a 24hr clock. U can control the light and dark periods independently. Like 16hr on 12 off or whatever combo u want. This can increase your yield or speed up ur crop. Does this answer your question? I think the timer is expensive like $200? But I'm not sure

you can tweek the cycle for more dark not less, all your gonna do is stretch out you flower cycle with growth but nothing that couldnt be achieved with a longer veg, might as well veg longer store more energy

my advise going less then 12hr of dark is a bad idea,i have heard of 6hr light 12hr dark so in a 24hr peroid the 12 light and 12 hr dark has been achieved , some thought that the plant only grew or would uptake nutes for 6 hrs then cut back growing or uptake of nutrients

There should be no reason for this not to work. That's like saying giving a vegging plant an extra 3 hours of light on a 24 hour schedule won't increase the growth rate. It's simple, your giving a flowering plant 15 hours of light in a 24 hour period in a way that won't send it back to vegging again.

Definitely going to give this a try on my next grow.

all im saying is you can achieve the same effect by having a longer veg time with proper manacuring and not have to use anymore power, its seems a waste of money

I started an experiment with 18 hour days under flowering(9/9) the plant was flowering just fine 3 weeks in when i switched it back to 12/12 as i got worried about yeild. It actually ended up being my best quality ive gotten but i doubt the cycle had anything to do with it

plants need routine like natures photo cycles just remember any tweaking should either be gradual or all at once with limited changed, good luck by the way

haulinbass said:

I started an experiment with 18 hour days under flowering(9/9) the plant was flowering just fine 3 weeks in when i switched it back to 12/12 as i got worried about yeild. It actually ended up being my best quality ive gotten but i doubt the cycle had anything to do with it

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people veg 18-6 so ya no wonder it turned out the good, or did you mean 18/12, i like to do my own tricks, darkness for 48 hr before the flip and 48hr darkness before the clip

I would also like to see another test, out of curiosity, just to see the results.....something like 14/10 vs. 10/14, to see the difference in yield and finishing times. Yes, I know it's a different concept that the test mentioned above, but it's easier to do. I'm just curious to see if 12/12 is the optimum, as recommended widely, or not. So,...might as well throw 12/12 in there too, I s'pose....lol

Night time is when all the magic happens.....why would you want to do this?

Samwell: you can tweek the cycle for more dark not less, all your gonna do is stretch out you flower cycle with growth but nothing that couldnt be achieved with a longer veg, might as well veg longer store more energy

all im saying is you can achieve the same effect by having a longer veg time with proper manacuring and not have to use anymore power, its seems a waste of money

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I don't think you quite understand what I'm proposing here.

I know from real-world observation that most plants will flower with well under 12 hours of dark time. Your saying it isn't true doesn't make it untrue. Yes, there definitely is a minimum dark time you can't go under, and its probably going to vary a bit based on strain, but I suspect 9 hours of dark time probably is enough for many common strains. It might even be possible to go less than that.

Again, what I propose uses absolutely no more power than a regular grow. . .that's the whole point. Increasing vegetative time completely defeats the purpose of shortening the days.

For BTG: Yes it "should" work, but that doesn't mean it "will" work. Plants do have circadian rhythms and its quite possible that 21 hour days will mess them up enough to prolong flowering, or have other unintended consequences like decreased yield (or hey. . .maybe increased THC!). Again, in theory there should be no real benefit to this unless you're doing continuous or consecutive harvests.

potpimp said:

We're not asking you to do a control group with comparative data, just do a casual test to see if it works, a proof of concept. Personally I think there are easier, better, more natural ways to increase yield, but this is interesting and I would love to know how it turns out.

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What sort of ways to increase yield are you referring to?

Doing things like adding nutrients, hydro-growing, LST, SOG, etc are NOT incompatible with artificially shortened dark periods. Presumably you'd still be doing all those things when running 12-9 flowering days. They're not mutually exclusive.

Again, the purpose of this is NOT to increase the yield per plant. Its to get the same yield just in less time.

In a nutshell, by reducing "unnecessary" dark time, you'd be cutting a week off your total flowering time, and having slightly faster harvests. Any increase in yield you'd have, would be because you can do more harvests per year. Each harvest costs the same in terms of energy used.

To be clear, I can't personally test this because I'm simply not growing right now. I'd rather not get into details, but I'll add that I don't see myself being in a position to test this anytime soon.

A potential problem with a proof of concept is that without a control, you could theoretically run the experiment, actually have a "success" and still not really know if it worked or not.

Obviously, if the plants all turned hermaphrodite, or didn't flower, or never finished, or took the full expected calendar time to finish instead of finishing a week early, then we'd know this doesn't work. . .at least not with the given strain it was attempted with. (Strain almost certainly does matter here).

If I took a strain that usually takes 65-75 days to finish, and got it to finish in 70 12-9 light cycles, then this will have taken me 63 calendar days.

That would be a proof that this can work *if* I knew for sure that the true finishing time was supposed to be 70 days. As you probably know, the advertised finishing times don't always square with the reality.

But lets say I took that same strain and now it takes me 74 or 75 12-9 cycles to finish. Now it will have taken me 65 calendar days to finish up, and the results would be a little ambiguous. Someone else will just say that I could have had the same exact results had I just run 12-12 normally for 65 days, and without a parallel control, I can't say for sure that they're wrong.

And no matter how long it takes to finish, wthout a control, it would be impossible for me to know if 12-9 cycles affected yield and by how much (either in a negative or positive way). Thats absolutely critical, because again, otherwise, someone will just claim (without evidence) that yeah, maybe I finished a week early, but I would have grown oh so much more had I gone 12-12 for that last week.

haulinbass said:

I started an experiment with 18 hour days under flowering(9/9) the plant was flowering just fine 3 weeks in when i switched it back to 12/12 as i got worried about yeild. It actually ended up being my best quality ive gotten but i doubt the cycle had anything to do with it

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Assume nothing. . .for all you know 9-9 lighting forces plants to increase THC output.

This is obviously different than 12-9, but too bad you didn't take this to the end to see what happened.

There is another issue at play, that supposedly plants react to decreased light hours by finishing up their flowering faster.

I think you probably could take a plant successfully to harvest faster under 9-9 lighting, but since the plant would be exposed to less overall light during flowering your yield would probably be reduced proportionately.

If maturity is entirely day dependent, then in theory you could shave off fully 25% of your flowering time this way. Even if yields were reduced proportionately, I could see situations where this might be advantageous.

For example, lets say you wanted to try some Sativa strain with an absurdly long finishing time. Or lets say you needed to finish a grow by a certain calendar date, etc.

jawbrodt said:

I would also like to see another test, out of curiosity, just to see the results.....something like 14/10 vs. 10/14, to see the difference in yield and finishing times. Yes, I know it's a different concept that the test mentioned above, but it's easier to do. I'm just curious to see if 12/12 is the optimum, as recommended widely, or not. So,...might as well throw 12/12 in there too, I s'pose....lol

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Given how easy it is to do, I'd assume this sort of test has been done already. . multiple times.

If 14-10 (or 10-14) were significantly better, I suspect everyone would know it, and would be using it already, though again, this is probably strain dependent too.

My guess (and its just that, an educated guess) is that what you'll find with something like 10-14 is just reduced yield. Remember, supposedly plants do respond to reduced light by flowering faster. But whether that's true or not, in a given number of flowering days they'd be getting less light under 10-14 and would probably yield less. Again it might be worth the decreased yield to finish faster, in certain circumstances.

14-10 might increase yield over 12-12, but with long days, I'd expect that the overall flowering period would probably be lengthened. That might be fine if you're only doing an occasional grow, but it wouldn't be acceptable for a commercial grow.

12-12 is probably the default flowering time for most growers as a compromise between yield and reasonable finishing time.

do a test run

you can find out the fun way, but remember the the natural cycles of the sun slowly progresses from 12/12 in spring to the summer solstice and then 12/12 agian then to 14 hrs of darkness in late october

this is based on cali, night and day hours, so best possibles light and growing light in US at least

12-12 is probably the default flowering time for most growers as a compromise between yield and reasonable finishing time.

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Well yeah, that's what logic would tell you or I, but I'd like to see the actual numbers. Time to move to a different state, and do some testing, eh?

12 and 12 is that way becauese of its efficeincy, indoor and outdoor have the same objective but different methods, indoor is how many cycles you can get in a year, i do about 6, and out door is how big can i get it

and how healthy can i keep it, i mean thats a little simple but those will get you good yields with the obvious reason also being

strain , grower skill, style, light, nutrients and manicuring, mediums and experience