24/7 for Autos?

Have run autos in grow tent both 24 hrs/day as well as on an 18/6 cycle. In both cases plants have done fine. Seem to be two schools of thought. One says Autos will be Autos and therefore you don’t need to give them a dark cycle like a regular photo sensitive plant. The other says the plants want some rest and a respiratory cycle just like their large sisters.

two grows over the winter here in a cold climate. In both ran 24 hrs under lights. First batch were beasts. Second batch were quality but both the plants and yields were down a good amount. Same strains, soil, nutes, etc. My first inclination is batch #2 had really low humidity since they grew through January and February. However, I am also questioning whether they were reacting to constant light.

Anybody have a strong opinion for which you can provide either some meaningful science or clear cut personal experience?


DLI. There is only so much light the plants are capable of processing according to the environment they’re in. If you’re hitting their maximum intake of light, they aren’t using the rest, which means you’re spending money running lights that you’re plants are ignoring.

I prefer a sleep cycle.


Plants do all the photosynthesis stuff with lights on and conversions from salts to sugars ect at lights out. So if light always on there is. O rest period for the plant at all constant absorbing light and not having time to convert it may not be a good thing. I only run my lights 24 8 for the first 2 weeks at most then 18 6 from there on autos and photos both til photos r ready for flower then they get 12 12. So u say I’ve done both constant light the whole grow and a whole grow of 18 6 right?? Constant had less return u say?? What was the smoke report like. One more potent than the other one taste better look better smell better ect.

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18/6 everything needs rest happy growing my friend

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My thought is, the sun goes down everyday, they need the rest time. Do your leaves look kinda wilted late at night? That’s rest mode. No need to run 24 constantly. Sleep time is good.

Dr bruce bugbee says on one of his videos on YouTube that the plant needs to have a dark period for it to get the best results .but he also said that you can run a 24/7 light cycle if u wanted to and still get similar results but however it is a waist of power

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I think a lot has to do with what type of lights and wattage your running combined with the conditions that the plants are growing in.
I tried 18:6 for my autos, and with my lights they were exhausted at the end of the day and looked like they had not been watered in 2 weeks. This was every night. I backed down to 16/ 8 and between the extra two hours of rest and the two Less hours of light, the plants stopped looking exhausted and definitely showed improved growth.

For my experienced i run auto and my first growing was 18/6 on sativa was good normal but i find run 24/7 was better for my so i don’t be buy stuff and change my light schedule so in autos is all about electric bill if you can pay you bill run them 24/7 if is to high run 18/6 or in flowering change to 12/12

This is exactly what I’m looking for. Lots of good info here. After reading the article I come to the conclusion that Autos and feminized are, in fact, different animals when it comes to photosynthesis. There really isn’t a downside to the Auto plant when I run 24 hour light cycle. It may increase the ultimate yield because the non photoperiodic genetics allow it to continue to do everything it needs to do even without the light. However, when taking into account the marginal increase in yield, it sounds like it’s not necessarily worth the extra electricity. Plus, I would presume, wear and tear on the lights is a factor. LEDs don’t cost a lot to run but they are pricey. So it seems that it shortens their effective use running 24 hours as opposed to an 18/6 cycle.

Bottom line is it sounds like there are opinions on both sides which make sense. The difference in what gets harvested in terms of yield and quality might be a tempest in a teapot. If you’re growing for profit, going constant light is an exercise in diminishing returns. If you’re growing to simply try to do the best you can, a 24 hour cycle might get you a bit more in the end. (It should be noted that if my plants showed signs of light stress, as some of you have mentioned, I’d absolutely give them a break.)

So this brings me to a related question (of my own consistency or sanity): just started thinking about whether it made any sense to run those Autos 24/0 and then stash them in a cool dark place for a couple days prior to harvest. I guess I should probably pick one approach or the other. Either light matters in an Auto. Or it doesn’t.

Fascinating stuff.

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Excellent summary.
I’m going to add one more factor into the mix. Mostly because I’m dealing with it myself at the moment. I’m using my lights for heat, as well as the obvious. If I turn them off, the tent will drop to about 62 in a matter of an hour. So I’d have to run a small heater to keep the temperature up.
At that point you loose the cost savings angle.

Much to consider….
I appreciate the thoughtful knowledge on this forum.

I’m growing in a northern climate, in my basement. So I also deal with a temp issue during the winter. I keep a space heater in the room but the environment in the tent is always different from that outside the tent. I make sure to have carpet or something to insulate on the floor under the tent. Also use heat mats under the fabric pots to keep the soil warm enough.

My biggest challenge is that when it’s cold, it’s also very dry. Particularly tough to get those seedlings to consistently thrive. That calls for a humidifier in the tent until the plants are well into a flowering stage. Humidifiers need distilled water which also costs. Been able to mitigate that a bit by recycling the water from the bathroom dehumidifier where we shower.

One thing leads to another. Unlike custom designed grow rooms used by professionals it’s always going to be a challenge to get the best environment possible to maximize results. That’s frustrating in some ways but if it was easy, everybody would be really good at it. The challenge is what I enjoy.

My philosophy is that each of us should determine how hard we want to work and how much we are willing to spend to get results we want. Depends on your ultimate goals. I just give it away and am not too concerned with some of the ancillary costs. If somebody is growing for profit, it’s a different calculation.

The great irony of this obsessiveness is that when summer comes, I grow regular fems plants outdoors. In that environment, you can toss all that control right out the window. And I just roll with it.

Case in point: roughly 2-3 weeks prior to harvest last fall, we had a small tornado skip over us. Came out the next morning to find all those huge beauties in a sopping pile. Took a couple of us over 7 hours to get everything staked up again. Saved most of it but it was touch and go.

So in the grand scheme of things I guess I’ve decided it’s a process. Control what you can control. Try not to fret the things you can’t. Sometimes the results will surprise you. Sometimes they disappoint. The trick is to just keep ratcheting up that worst case scenario and move on to the next grow. It’s a blast! Weighing up something you’ve never managed previously keeps me coming back.

I too am in a northern climate and growing indoors, in an unfinished basement. So your thought process/troubleshooting is very familiar.

I am a lifelong outdoor herb/veggie gardener. So I also understand the idea of controlling what you can. Rabbits are my on going nemesis.

I’m currently working on my first grow of this plant. If I end up doing a grow journal, I’ll tag you @itcmdr. I appreciate your similar experience and philosophical views.
Thank you for sharing them.

I would appreciate that. I always say I’m going to journal but then get lazy. Makes me mad when I make the same mistake more than once but I still do. When I started, everybody talked about just pay attention to what the plant is telling you. So I’d end up on the internet getting completely conflicting takes which didn’t help much. Kind of like using WebMD and thinking you have Legionnaires Disease. But like many things, over time and failure, you know what they’re trying to say.

The good thing about the indoor grow is that it’s strictly Autos. Given the time and effort to complete them, failing is not a big deal. I have two tents so normally harvests are staggered. That allows for some experimentation side by side. If that one wasn’t happy, did the changes made to the next batch seem to make it better?

I’ll plan on starting my outdoor plants in another week or two. The plants nearing harvest will tell me when they’re ready to get chopped and make room. Weather will determine when they can go outside. I have been lucky with critters since I live in a fairly rural area. Because I grow in 30 gal fabric pots, rabbits can’t/don’t bother them. The deer and squirrels scare me to death so I always keep the perimeter of the grow site well coated with pest repellent.

I treat my outdoor grows with NEEM Oil. That helps to keep insect pests off the plants. It’s a natural oil that coats the plant and I wonder if it also helps make the plant unpalatable to things like rabbits. Sure couldn’t hurt to try. Just be careful of when you apply it since it initially magnifies sunlight and can burn the plants.

Or if you have enough time, you could take up the sport of falconry. Bunnies would decide there are better dining spots in the neighborhood right quick.

Last year my expectations were low, so I started twice as many plants as I really wanted. Everything thrived and I ended up with this huge mass of 12’ plants. I was stunned. No question they needed way more room to maximize yields, so my goal this summer is to grow fewer plants and get the same yield.

I also reflect on the fact that last summer was nearly perfect. The close call with the late storm really rattled me. Mother Nature can give or take. So my outdoor grow is going to put a significant emphasis on Autos in addition to the couple full sized. I look at it as simple diversification. If something bad happens, I have time to start again. With Autos, if you lose some, it’s not nearly the investment of time and energy as full sized. You just move on. It has the added benefit of getting to try different strains which is something I really like.