24 hr light cycle for photosensitive

Anyone know if its ok to give photosensitive plants like purplehaze under 24 hr light to start out for veg? Im tuna have some autos I wanna sprout after but im not sure if the 24 hr light cycle is ok for thew veg state of a photosensitive plant… Will having them on a 24 hr light cycle for veg, then switching to 12/12 to flower, will that cause issues with the photosensitive plants, maybe hermie issues?

I normally do 18 hrs light for veg maybe 24 hrs for first 2 weeks of plants life the 18 for rest of the veg state. for autos I keep that the whole time… but obviously im afraid if I have autos in the tent with my purple haze, that 12 hrs of light for them will drastically decrease the possible final yield. So I want to start them all on 24 to hopefully counteract some daylight hours they’ll be missing out on when I switch the light cycle for flowering my haze

No, you can give them 24hrs of light, although I don’t recommend it. Even my autos I grow with a dark period. Imagine you’re the plant, you’re busting your ass off 24/7. Now, wouldn’t a little break everyday be nice. When light comes back on, I always see significant growth


Also most root growth and conversions of chemicals happen in the dark. It might work for a week or 2 as the seedling has its own storage of nutes in the cotyledons. But once in veg all plants need a rest.


You can grow 24/7. It’s been proven by plenty of people that it can be done. A lot of people say that you will see diminished results, but from the articles and study’s I’ve read, this isnt true.


Hi @Aolelon thats sounds interesting , can you point me to any material on the subject. cheers


I am at work atm, I will try to find the study’s I read when I get home


Well for bud growth darkness is definitely important. Like Adelon said tho it is definitely not 100% necessary. You’ll still get fat buds with 24 hrs light I’m sure. And I know a lot of the chemical production or whatever happens during the darkness. But I’m just wondering in terms of hermie possibilities from switching a photosensitive from 24 to 12. But ya I guess it probably would be fine just not ideal obviously

You can only use 24hr light during the veg period with photoperiod plants, oas you need 12 hours of complete darkness to trigger the flowering function. You can use 24hr on Autoflowers just fine. Most people find 20/4 is better though.
If you do the research, it shows that cannabis does not need a dark cycle during veg to continue growth, and plants actually veg faster during 24hr lights on.
I cant find the exact study I read, as it was awhile ago. But googling will bring up a number of results of people having great results using 24hr compared to 18hr
A lot of the reason most people use 18 over 24, is to save on electrical usage.
Here is one article that I did have saved to my desktop

You ca however change the day in flowering. Keep the lights on for 24hr then off for 12hrs. As long as a flowering plant has 12 hours of uninterrupted darkness, before its next lights on schedule, to a certain extent, it will stay flowering, and some have even reported it to flower faster.
So instead of a 24 hour day, you’re essentially making it a 36hour day.
Cannabis plants are classified as C3 plants, which mean C3 gather CO2 only during the light period when they are photosynthesizing. During the dark period these plants only use oxygen for their metabolic life processes. They don’t uptake CO2, nor do they use it. As soon and as long as the light is on, C3 plants gather and use CO2 for photosynthesis.

C3 plants also have the ability to use higher concentrations of CO2 than what is found in the air. If the light is bright enough and the plants havesufficient nutes, their growth rate will accelerate from it(2000ppm vs. 400ppm of CO2), which increasesyield. They can do this continuously, without a dark period throughout the vegetative stage.


Wow, thanks for taking the time to post that. I will look into it some more cheers

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I’ve done 24/0 on autos, and didn’t see much difference in yield or potency from doing the normal light schedule for photos that I use which is 4wks 18/6, 2wks 16/8, and 2wks 14/10 before the 12/12 switch. I do it that way because when I switch to 12/12, I have plants that start flowering immediately and the autos have pretty much stretched by then. If you want to try it and have enough time before flower, you might drop gradually to 12/12 like I do. I think they would do fine if you go one week each at 18/6, 16/8, then 14/10. Just my opinion, of course @Essigba.

so I do plan on doing a gradual decrease like that, but is that schedule your doing generally for sativa/longer flowering period plants. cus Ive got the pure indica strain from ilgm that im using right now and I think Ill have to try doing that on a bit of a tighter schedule like over 10-11 weeks rather then full 3 months.

but so anyway, ya I do know to do the gradual change cus its just more natural for the plant in general, the amount of sunlight doesn’t just reset in the wild from 18 hrs to 12 all of a sudden so I obviously see that being beneficial. And even more so for the autos that I have in the tent growing along side the indica. cus then they’ll be getting a few more hrs of light then 12 for an extra week or too as well. Not sure if you were referring to both there @OldSkunk , the fact that it would be better for the autos in the tent too. But I definitely will try going about it like that.

would u still recommend that layout for a plant like the pure indica? I think id probably have to shorten the whole timeframe by like 2 weeks right?

I grow heavy Indica plants myself because of the type of pain I have. It is the heavy sativas that grow slow for me. I do like their high though.

@OldSkunk I don’t think you got my ? tho lol… so when u make the switch to 12/12 after the gradual decrease… how long do u generally have to grow them under 12/12 for… you said they start flowering faster because of the gradual decrease before the actual 12 flip. but then how long after do your indica generally take to be ready for harvest? and does it ever affect quality of buds? or do you just get bigger yields with the same quality thc?

like if I wasn’t doing gradual decrease id do like 24/0 more likely 18/6 for 4-6 weeks then flip for another 6-8weeks depending on how long they were in veg and based on other factors of the individual plant obviously, but in general?

Heavy sativas about 12 weeks of flower time. I only grow ILGM seeds and because I mostly grow heavy Indicas, I usually flower for 8 weeks. I did let Strawberry Kush (heavy Indica) go for 12 weeks on one grow and wasn’t a big enough extra yield that I would do it again. Does that answer your question @Essigba?

Your plants wont begin to flower until they have at least 12 hours of darkness, so if you took 4 weeks after you started to decrease from 18/6 to 12/12. Your plant wont begin to start flowering until that 4th week when your plant finally receives its first night of 12 hours of darkness… you may see some less stretching, or see them actually flip into flowering mode faster, a couple days instead of maybe the week, week in a half that it normally takes. But there are other methods to do that as well.


To add to what @Aolelon is saying, they need to be mature enough as well. Usually at least 4 weeks old before they’ll flower. Sometimes a little older.


Did not know if I should post this here or not.
Anyway I ended up with some feminized black apple Hitchcock seeds that i germinated and I had one come up about three o clock today and I have a couple white widow autos in the tent already on 18/6. My lights go off at midnight tonight and I don’t want to change their schedule. Will it hurt the seedling or do I need to
Change the schedule.

Ur good