24/0 vs 20/4 light schedule?

[FelipeBlu]

Indeed, even during flowering, if you determine (through multiple grows with the same strain) that you are happy with the final product when bloomed at a DLI of 45, and you can safely provide 1200 PPFD, then you could turn the lights off after only 10.5 hours.

 

[AKgramma]

Not so fast.
While it dont HAVE to have a dark period it is used by them for needed processes. I have grown in 24/0, 20/4, 18/6 and my plants have been bigger and healthier with 18/6 than any other schedule every single time. If you are using weaker lights then maybe your mileage may vary but yes, they do use the dark cycle.

The dark cycle is an essential part of their metabolism. During the "day" they are photosynthesizing and storing nutrients. At "night" their metabolisms switch to usage of those nutrients to grow, repair and replace old tissues, or make the major switches as they age towards maturity.

This is why you see noticeable changes when you check them in the "morning" when the lights come back on. You CAN provide them "food" around the clock, but that is not the environment they evolved in. All living things need that resting period to maintain health and perform at their best.

This from an Old Lady who 1) has a degree in Biology, plants being my major focus, and 2) Many decades of growing vegetable gardens in Alaska, where the day length changes daily. Yes, we grow some enormous veggies that were bred for growing quickly and very large, but the natural biota has adapted to the unique seasons we have here.

For a short/seasonal grow, following the light cycle of the area where the landrace ancestors came from (closer to the equator), a more natural light cycle is healthier.

FWIW

 

[AKgramma]

When it goes into a dark cycle during daylight hours, are those daylight hours being wasted? I wonder.



I might do in a week or two if looks like handling it. I slipped it into a 13 routine last night after an 18/6 hour day. So far, up to now, it's had a 12 hour dark period, interrupted for an hour with light in the middle of it, and is now just finishing a 12 hour day. It's nearly done a full cycle. It's only just starting its second proper set. The change, I hope, shouldn't upset it too much at this stage. This is going to be a 4-way-gas-lantern-scrog. Should be fun.

I had a strain whose males flowered during a gaslight schedule, way ahead of the ladies he was supposed to pollinate. it was a surprise to be greeted in the morning by an overnight appearance of stalks covered with pods!

 

[LiberalThinker]

I had a strain whose males flowered during a gaslight schedule, way ahead of the ladies he was supposed to pollinate. it was a surprise to be greeted in the morning by an overnight appearance of stalks covered with pods!

Thinking positively: if you need to flower a male fast, that's a way to do it.

 

[DaddyKush]

Just as plants need CO2, the roots require oxygen... and the dark period is when they get it. Roots grow mostly during the dark cycle, so having a few hours of dark in every 24-hour period is highly beneficial even if you can't see it. While it's absolutely true that 24/0 won't technically harm your plants, doing it does not allow them to perform as optimally as they should.

Ultimately, we're trying to simulate the natural outdoor environment which cannabis has grown in for thousands of years. That natural environment has never featured 24 hours of uninterrupted light and it never will, not until we start growing on other planets I suppose. But for anyone who insists on ignoring the science, causing unnecessary wear and tear on your equipment, while also driving up their electricity expense, go ahead. It's your money and you're free to waste it.

 

[fanleaf]

Yes, please explain in terms of cannabis being a C3-type plant.

Exactly, I'm hoping he can explain though..

During daylight the light energy is converted to sugars, starches and carbohydrates. As the world renowned biologist Elaine Engham calls these "cakes and cookies" since what the plant converts light into is the same ingredients (starches,sugars and carbohydrates) to make cakes and cookies. While the plants are making "cakes and cookies" during lights on, this is hard work that requires lots of energy to do. Then, after the plants leafs make all of those cakes and cookies it gives those cakes to the soil via exudates. So, now we know that what is expelled through the roots CAN be sugars, starches or carbohydrates or any 2 of those or all 3. The magic is that whatever nutrient the plant needs the most at that time the plant will expel more of 1 of those 3 because just for example if the plant needs more Nitrogen it may expel more starches because starches may be the 1 that when the roots get that it knows microlife that specialize in making N available use the most. Does that make sense? Now, I dont know that starches are the signal for more nitrogen as I just threw that out for an example. The bottom line is that what the plants roots expel is selected special for what the plant needs in return.

This all takes time and it seems to me like if there is no dark cycle there would be a point at which the "need" for something up top cant be kept up with because the need is always increasing without giving the top side a break for the bottom side to catch up because it takes time and lots of energy for exudates to be processed and out of those exudates new available food created.

 

[FelipeBlu]

Has anyone found a difference between 24/0 veg, 20/4 and 18/6? While vegging, cannabis doesn't require a dark period so is it just slower growth and better on the electric bill to give a dark period?

Getting back to the OP, who states their opinion regarding whether cannabis needs a dark period or not (so perhaps we can move on from that fractious subject).

Yes, there can be a difference between the three lighting periods, but it depends more on how much light can be provided, than the absolute schedule. Past a point, you may save money by turning the lights off. But many cannabis plants have been vegged under 24 hours of light with perfectly acceptable yield, taste, and high.

 

[Imakiwi420]

Has anyone found a difference between 24/0 veg, 20/4 and 18/6? While vegging, cannabis doesn't require a dark period so is it just slower growth and better on the electric bill to give a dark period? Would also help with temps depending on grow environment. All input is always appreciated!

I have tried both plenty I usually go 24/0 in our colder months here in New Zealand and 18/6 in the warmest time but the only difference I have noticed is 18/6 is better if you plan on stressing or training in anyway they seem to recover a lot faster with some dark but that’s just my opinion. But as for growth I don’t see a lot of difference. I recently moved to 3gallon airpots and they definitely have made a big difference in growth so I do recommend them but others may disagree

 

[Yankeerunner]

Has anyone found a difference between 24/0 veg, 20/4 and 18/6? While vegging, cannabis doesn't require a dark period so is it just slower growth and better on the electric bill to give a dark period? Would also help with temps depending on grow environment. All input is always appreciated!

I don't have a lot of experience, but I veg'd mine with 24 constant and with pretty good success.