Auto light schedule 24, 20-4, 18-6

Anyone done testing on autos for the best light schedule?

Why 24? 20-4? 18-6? What happens if I run 19-5?

Maybe I like odd numbers more then even.

At the end of the day, do what works best for you. I can't say who or when,but I do remember hearing on a couple podcasts that 20/4 was found to be ideal. I belive that the reasoning I'd that any gains in yield between that and 24/0 are negated by cost of energy and electric.

I'm curious about that, too. Right now I'm growing a Hulk Berry Auto with 24 hours. I don't know what will happen to this plant. It's just a house plant so there's no light control.

I would like to get something out of this plant but with it being in the house with no light control I hoping that it doesn't go hermi.

I googled "what happens to marijuana if grown under 24 hours of light?". I didn't get much info that I really wanted to hear. Best at 18/6.

There's a point of diminishing returns; a 24/0 plant certainly doesn't grow 33% faster than an 18/6 plant.
24/0 makes sense only if there's no way to maintain a reasonable dark-cycle environment

Billy the Mountain said:

There's a point of diminishing returns; a 24/0 plant certainly doesn't grow 33% faster than an 18/6 plant.
24/0 makes sense only if there's no way to maintain a reasonable dark-cycle environment

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Lost my grow room to my wife's outdoor garden. It's full of her outdoor plants and bugs.

I just wanted a house plant so started one that sprouted on Dec. 30. It's getting a lot of LST and being made into a bush.

This thread just really struck my interest at the time. The best answer so far is that the plants need rest.

I grow my autos at 24/0 until well into veg and then go to 18/6 to 21/3, depending on how much DLI I want them to have. Regardless of the photoperiod, I feed my plants as much light as they can tolerate.

Research demonstrates that cannabis yields increase in an almost linear manner as light levels increase. Depending on how you want to cost your grow, it's hard to come up with a scenario where increasing the photoperiod is not an economically sound move. The primary reason for that is that, in most places, cannabis is extremely valuable so the marginal increase in cost is significantly outweighed by the marginal increase in income.

I've attached a paper that discusses this issue.

Re increase in crop yield, the "Frontiers…" paper provides additional detail. The change in yield is shown in the table I've created, below:



For each 50µmol of PPFD, increasing PPFD from 600 to 800 showed an increase of 5.2+4.9+4.7+4.5≈20%. Going to 900µmol, resulted in another 8.4% increase for about a 30% improvement in yield by increasing PPFD from 600-900µmol. That's a 50% increase in electricity cost for a 30%± increase in yield. I cost my electricity at 40¢ per KWh and an ounce of weed is at least $300, with premium weed going for at least $500 so the increase is well worth it for me. If I was living in Colored, for example, I'll pack up my tent since weed is so cheap there.

I find it hard to believe that some dark hrs are not beneficial, all living things require some rest.

I normaly grow autos under 24hr light. They usualy take longer to finish but i find they yield much bigger for me under 24hr. I find them more potent aswell. Dont ask me the science behind it as i wouldnt know. However i do know over its flowering cycle the plant is harvesting about a 1 3rd more light, they take longer and develop more complex and potent. With 18on and 6off or what ever i could allways pick up a dullnes somewere in the high on autos but that dont seem to happen with all the extra light hours and extra develpment time.

5thwheelrvgrower said:

Anyone done testing on autos for the best light schedule?

Why 24? 20-4? 18-6? What happens if I run 19-5?

Maybe I like odd numbers more then even.

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My auto likes 20/4. I tried 24/0 but she didn't like it.

My little Hulk Berry Auto is really doing well under 24/7. I'm not an indoor grower as a general rule so there's nothing to compare. I think maybe I overdid it on the LST. It's now a very dense bush at 19 days from sprout.

I think it likes the 24/7.

I ran my last grow 24 hours and was happy with the results. The Mephisto page recommends running 24 hours to maintain a consistent environment, which is very compelling for me in the cold winter basement. May start adding darkness during the summer grow, though running 24 hours led to my best results yet. I’m planning the same with the current grow.

I'm on day 45 of 20/4 with my second run of 3 Bears OG. Maybe I'll try 24 hrs and see what happens, it would give me more consistant enviro. Anyone have thoughts about changing half way through a run?

1212ham said:

I'm on day 45 of 20/4 with my second run of 3 Bears OG. Maybe I'll try 24 hrs and see what happens, it would give me more consistant enviro. Anyone have thoughts about changing half way through a run?

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Only one way to find out!!!!

1212ham said:

I'm on day 45 of 20/4 with my second run of 3 Bears OG. Maybe I'll try 24 hrs and see what happens, it would give me more consistant enviro. Anyone have thoughts about changing half way through a run?

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I don't know but would be curious to find out. If you do it post your results.

1212ham said:

I'm on day 45 of 20/4 with my second run of 3 Bears OG. Maybe I'll try 24 hrs and see what happens, it would give me more consistant enviro. Anyone have thoughts about changing half way through a run?

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Not a problem by any account I’ve read.

I doubt I'll see a clear difference, but I might try it, thinking of changing feed times anyway. Feeding every 2 hrs, might go to 3.

I currently have a jack herrer I ran 24 7 all the way thru till week 9. Buds started week 8. Running 19-5 now. Will see if the buds get thick and heavy with the rest period. From everything I read buds grow beat with some darkness. I have no idea. But I am trying 19-5 if the temps maintain above 70. It is winter so we will see. Currently the grow room fluctuates from the lowest when it was -12 67 degrees to 85. And the plant looks really healthy.

altaran said:

Yeah, ive only grown autos for the last 8 years..... First time on photos, and only 4 weeks into flower and im already more impressed.

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This is almost my first time with autos. I dropped a seed once but wasn't really interested in growing a few ounces (maybe) with pounds growing out in the garden.

Weeds says this is my pet plant. I was thinking about changing to autos for my next grow.

I ended up with 3 ounces out of the jack herer but.switch back to 24/7 due to environment control.

With auots 24/7 for me