24/7 vs 18/6

[South Sierra Dude]

Some one asked today if 24/7 or 18/6 is better in veg. I am unaware of a compelling reason to turn the light off. The only answer to the question I've heard is anamorphic or based solely on things like: "It's what I've always done. In leaving my light on the whole time so far this grow. Both previous I used 24/7 for germination, 18/6 veg, and 12/12 flower.

So is there a physiological reason to provide darkness in veg?

[Potted]

None I can think of,I've been doing that very thing from seed to veg.under t8 lighting all the way to flower stage than switch to flower 12/12 under hps 600w flower.

[Tika]

Well I always do veg 24/7. Because I can't navigate less. Been told by Master grower here the plants need rest. I get that but can't oblidge.
no help here but good thread and I'm eager tonhear

[9fingerleafs]

I've heard even under 24 hours of light the plant is going to "rest" whenever it needs to in order to do the processes that happen during night (mainly root developement and other root processes) and this also supposedly happens with any plant in any light cycle. And that's why sometimes they don't seem to be so perky with no apparent reason. I don't know how true this is but it kinda makes sense there's a bunch of things they gotta do besides turning light into sugars

[South Sierra Dude]

Indeed other things. like moving that sugar around the plant.

[South Sierra Dude]

Cool. I thought it was popular. I'm still a total newbie.

[alltatup]

One good reason to turn em off is to avoid over-heating plants in the hottest part of the day.

[South Sierra Dude]

I have considered this bit. It's about to get hot where I'm at.

[Weed Pharma]

I recall that-18/6 is the "standard", as somewhere around 17 hrs is the point where the expense benefit ratio starts to fall off.
So while you may see an improvement in growth- roots or otherwise- the cost to get that improvement doesn't justify the gains. That said:

I use 18/6 for the mother plant.
I use 20/4 for auto's.
I use 24/0 for germination and 24 hrs beyond sprouting.

[South Sierra Dude]

I'm 24 hourss past my final sprout and it's getting warm in the dessert. I'll keep it up till the swamp cooler can't keep up.

[Weed Pharma]

Going to try a 16/8 schedule for my mother plant and clones- as I am in no rush for them to grow-yet!

[NebulaHaze]

I've done both extensively and I think both schedules work great. The differences aren't huge, but here are my thoughts on the topic:

• 18/6 is better if it gets hot because you can have the six hours of darkness be during the hottest part of the day. It can also be a good choice it your electricity gets really expensive during certain parts of the day
• 24/0 is better if it gets cold because you can leave the lights on all day to keep plants warm. I've heard of a grower choosing auto-flowering strains because they wanted to be able to leave their lights on 24 hours a day so they could keep the plants in their cold garage without having to use any extra heating
• 18/6 is easier on the plant. If a plant is stunted or struggling, they seem to be able to recover better if they get a dark period. If I've got a sick vegetative plant, I'll put it on 18/6 and raise the light for a few days until it's doing better. The lowered light levels and fewer light hours reduces the amount of "work" the plant has to do each day (its main work is turning light into energy) so it can focus on vital plant processes and recovery
• However, with good temperatures and a healthy plant, you'll end up with somewhat faster vegetative growth under a 24 hour light schedule.
• Certain plants or strains react slightly differently, so what works best for one plant might not necessarily be the best choice for another plant. For example some strains are relatively sensitive to heat and light while other strains thrive in the same conditions!

I personally generally use an 18/6 schedule most of the time, in part because I live in southern California where it has expensive electricity during the day and often gets hot. I also like having extra resilient plants in case anything happens. A few extra days in the vegetative stage doesn't really bother me for those benefits.

That being said, I feel like the overall differences in growth and health are relatively small and depend quite a bit on your plants/setup. I think that's partly why it's hard to get growers to agree!

[Weed Pharma]

NebulaHaze : Yes, no two grows are the same and using lights to control environment is a great tool for growers and often overlooked.

[PaganRich]

For me, running 3 x 600 lamps is expensive and also has issues around heat, light, etc plus I figured there should be times for chill time especially after just being watered so I plump for 20/4 until 12/12

[South Sierra Dude]

So far middle 70s. I'm eaning your way by the solstice I think.

[furrysparkle]

My current grow I'm running 6/2 x3 cycles a day and it seems to be helping at least with the seed.... my last grow ran 24/0 due to not having a timer during veg