18/6 or 24?

I haven't used this site in forever lol but man this one kinda has me stumped. So the internet says you can run photoperiods on a 24hr light schedule, but a couple of my friends say it will mess them up. I know everything is different from strain to strain, but in general if it's not a strong light for the 24hrs i should be good right?? I really want to refrain from moving plants for a sleep period while i already have some flowering.

You can do 24/0 no problem.. They really grow!

I run 24 hours the first 2 weeks of sprout. Then 18 after. And no. Nothing will happen. They grow. And grow much faster than the added dark cycles

My plants get light fatigue at 24/0. There’s no place on Earth where cannabis grows in its natural habitat that gets 24/0.
18/6 works best for me.
YMMV.

Mrdoty said:

I haven't used this site in forever lol but man this one kinda has me stumped. So the internet says you can run photoperiods on a 24hr light schedule, but a couple of my friends say it will mess them up. I know everything is different from strain to strain, but in general if it's not a strong light for the 24hrs i should be good right?? I really want to refrain from moving plants for a sleep period while i already have some flowering.

Click to expand...

You can use 24 on, but my plants always look/become healthier using 20/4 or 18/6.

Mrdoty said:

I haven't used this site in forever lol but man this one kinda has me stumped. So the internet says you can run photoperiods on a 24hr light schedule, but a couple of my friends say it will mess them up. I know everything is different from strain to strain, but in general if it's not a strong light for the 24hrs i should be good right?? I really want to refrain from moving plants for a sleep period while i already have some flowering.

Click to expand...

You can run 24/0 for photoperiod plants in veg as long as you don't exceed their DLI. Otherwise your plants will experience light stress.

18/6 is where you wanna be but to answer your question you can run 24/0. I was educated in plant science an you possibly could be looking at potential light stress. Like most living things on earth they require some time of darkness a consistent break in light will allow your plant a period of rest. Why change light cycles multiple times during the life cycle. Just my thoughts!

twentyeight.threefive said:

You can run 24/0 for photoperiod plants in veg as long as you don't exceed their DLI. Otherwise your plants will experience light stress.

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BTW ^^ this is the correct response

I'll repost this here:

I try hard to avoid this subject but it keeps rearing it's head. So here are some of my thoughts on this. Also if you run 24/0 and are happy with it, that's great keep it up.

Actually I believe plants need at least 4 hours of sleep to use O2 for repair and regulation and as our lights get stronger they will need that off cycle even more. So far cannabis, a C3, can SURVIVE in 24/0 but if you look at studies of another C3 plant (tomatoes) actually get sick under continuous 24/0 as they can't clear the starch in their leaves.

In the simplest analogy humans are omnivores we can eat anything and survive. For example you could eat candy bars and survive but you wouldn't thrive. So I wonder as we push our light's performance how much is that extra four hours giving us? Is it measurable?

Cannabis isn't a tomato and it has a higher ability to flex to handle the higher light but I think as our lights get stronger (and the LEDS are doing that) I think we may start hitting the EPL barrier. Here's the simplest references I could find.


What happens to a plant that is kept under constant light?
Can a plant grow under constant illumination?
www.researchgate.net

Guido Bongi
Italian National Research Council
"The effect of continous lightning on photosynthesis depression is specific. In all plant that operationally accumulate starch in chloroplasts, even in the afternoon it has been measured a fall in photosynthetic rate. You can well build up a lethal response if strong light is added continously. Tom Sharkey but also Seeman, Berry, Flore described several cases in Plant Physiology, JASHS and PNAS from 85 to 95. This has been called end product limitation, EPL, and it is due to lack of phosphate recycling from chloroplasts stroma. Some tree can be affected by even by fruit removal and in this case it has been put in evidence a sink limitation. The common symptom is a gas exchange that is insensitive to CO2 level and Farquhar model incorporates this possibility. Specificity of EPL arises from the fact that sugar alcools can be efficient photosynthetic transporters and do not polymerize or subtract phosphate. Mannitol sorbitol galactitol and myoinositol are represented in fixation products of labelled CO2 in many plants and algae in a system that is in parallel to sucroseP photosynthesis, but not in all species. Possibly the lack of escape routes leads to CL sensitivity"

It's from here, in case you wish to read the entire trainwreck:

This is an interesting article that looks further into up and down regulation of production limiting factors (rubisco and TPU et al) https://academic.oup.com/jxb/article/70/20/5521/5589199

Hope that helps illustrate why I run in 18/6 and I have no problem if you choose to do differently.

I use 24hrs for the most part and 18hrs in the summer but both work fine.

If you google it you'll see plants don't sleep.

I do 18/6. I don’t see the need to spend more on my electric bill than I already do. Plus my lights turn off at the hottest time of the day helping keep temps in check.