16/8 vs 24/0 veg test, 18/6 included

So I've been growing for the better part of a decade and I've never done a 24 hour veg but have always advocated it's the best/fastest method to vegetate your plants. While the "test" is ongoing here are my results thus far. These are images of two plants, one grown under 16 hours of light, the other 24. I've done 18/6 but didn't notice much difference from 16/8 so I stuck with 16/8. The 24/0 is growing under a 250w CFL and the 16/8 was done under a 400w MH.

*Both plants grown in a waterfarm.

16/8 plant was grown ~1.5 years ago.

24/0 is current

Nutrients: Flora Nova series for both plants

16/8 used a 400w MH

24/0 using one 250W CFL

Temp/Humidity is the same 70-80F 30-50% humidity

Feminized seeds used

Day 1 16hr



Day 1 24hr



Day 5 16hr



Day 5 24 hr



Day 10 16hr



Day 10 24hr



Day 12 16hr



Day 12 24hr


As the 24 hour is still ongoing, I will continue to update if there's interest, but clearly the 24 hr is growing at a much faster rate than the 16 hour.

I'll keep an eye , seems like a nice experiment but are these the same strain? Are you feeding them ? whats the humidity and temps in both rooms? Are you using the same soil? perhaps if it was 18/6 the plant would be a big bigger, but who knows, let's see how this goes!

ive done tests using 18/6 and 24 hr light sced, both under the same light..i found as u the plant under 24 grew a bit faster, i grew same clones not dif seeds as that could be why ur test is showing a bigger difference pluss ur using different lights, try it again w/ same lights and same clones...anyways 24 hr clones grew a bit faster no huge diference, but when switched to flower the plant that had the 18/6 light sced will begin showing flowers by end of week 1, wile the 24 hr plant takes 2 weeks to show flowering..both finished in 8 weeks and yields were about the same...so in conclusion its up to u if u want faster growth in veg or faster bloom in flower..

ive also found if growing from reg seeds, your male to female ratio improves under 18/6 sced..under 18/6 i get 8 females out of 10 seeds, wile under 24 hr more often i get 50/50 5 males 5 females..all same conditions, only dif is the light sced...since my tests, i root clones under 24 hr light, then veg under 20/4 sced till flower, unless im growing from reg seeds then i veg under 18/6..all yields are roughly equal strain to strain..different strain, different growth rates and yields..clones= same growth rate and same yields. even 2 seeds of same strain can have different growth rates and yields..all side by side tests should be done with clones from same mom and all conditions same exept what ur testing for real results.

xtranger420 said:

I'll keep an eye , seems like a nice experiment but are these the same strain? Are you feeding them ? whats the humidity and temps in both rooms? Are you using the same soil? perhaps if it was 18/6 the plant would be a big bigger, but who knows, let's see how this goes!

Click to expand...

They are different strains grown at different times in the exact same tent with the same temp/humidity. I've done 6 or 7 plants under 16/8 and 1 under 18/6 and they all look the same at the same time from seed. This is the most dramatic difference I've ever noticed, so I decided to share. In veg, strains all typically grow at the same rate, you notice the strain variations in flowering. I always use Flora Nova series. I grow one plant at a time in a waterfarm, so it's not soil. Here's the one plant I grew under 18/6 at 10 days from seed, as you'll see it's basically the same as the 16/8 plant at 10 days from seed.

18/6 10 days from seed


I'll edit my original post to provide all of the information pertaining to the grow conditions ect.

mr2shim said:

They are different strains grown at different times in the exact same tent with the same temp/humidity. I've done 6 or 7 plants under 16/8 and 1 under 18/6 and they all look the same at the same time from seed. This is the most dramatic difference I've ever noticed, so I decided to share. In veg, strains all typically grow at the same rate, you notice the strain variations in flowering. I always use Flora Nova series. I grow one plant at a time in a waterfarm, so it's not soil. Here's the one plant I grew under 18/6 at 10 days from seed, as you'll see it's basically the same as the 16/8 plant at 10 days from seed.

18/6 10 days from seed
View attachment 3343406

I'll edit my original post to provide all of the information pertaining to the grow conditions ect.

Click to expand...

Ive always had good results w/ the gh nova series, but recently switched to the gh maxi series..All gh nutes are far better than other nutes as they always won in my side by side tests..consider trying maxi grow, maxi bloom by gh.. works just as well as the nova, better than the 3 part and much cheaper..ive used all but if ud like to dave a little cash try maxi, results should be the same or better than the nova..

Day 15 24/0


Day 15 16/8


Day 15 18/6



This is the 16/8 on the last day of the grow


This was the 18/6 on the last day of the grow

Interesting...Mr2

Sorry, but totally meaningless when you aren't comparing same lights and clones. This type of experiment leads to false or at least deceptive conclusions. Use the scientific method, we need to reduce this to where there is only 1 variable if you want to test that 1 variable.

Different strain, fail
Different light, double fail
Different time, tripple fail

Three strikes this experiment is out.

Cool to see difference

nomofatum said:

Sorry, but totally meaningless when you aren't comparing same lights and clones. This type of experiment leads to false or at least deceptive conclusions. Use the scientific method, we need to reduce this to where there is only 1 variable if you want to test that 1 variable.

Different strain, fail
Different light, double fail
Different time, tripple fail

Three strikes this experiment is out.

Click to expand...

What I'm doing is to see if a lower wattage light running longer would out veg a higher watt light running less. And based on that the answer is yes. To you it may not be, but honestly this is RIU. This place is littered with arrogance and I really, really couldn't possibly care less if you feel differently. The more light the plant has the better/faster it grows. Cannabis is an annual flowering plant, it doesn't need a light schedule to vegetate. It needs a light schedule to induce flowering, as well as "fall" light spectrum. If you're growing indoors you really should be doing 24/0. I've grown 16/8 and 18/6 since I started growing but personally I'm going to be doing 24/0 from here on out, if you don't agree that's great. I do not care.

BTW, your post does prove my point that rollitup is littered with arrogance. Are you the experiment Nazi? Do I have to get an authorization from you before I continue?

Three strikes and I'm out. Thanks for letting me know, umpire. (sarcasm)

Something else I would like to say. Given this is a website for 18+ we're all adults. I would hope that most adults have enough sense to realize running a 400w for 24 hours would out veg a 250w running for 24 hours.

mr2shim said:

What I'm doing is to see if a lower wattage light running longer would out veg a higher watt light running less. And based on that the answer is yes. To you it may not be, but honestly this is RIU. This place is littered with arrogance and I really, really couldn't possibly care less if you feel differently. The more light the plant has the better/faster it grows. Cannabis is an annual flowering plant, it doesn't need a light schedule to vegetate. It needs a light schedule to induce flowering, as well as "fall" light spectrum. If you're growing indoors you really should be doing 24/0. I've grown 16/8 and 18/6 since I started growing but personally I'm going to be doing 24/0 from here on out, if you don't agree that's great. I do not care.

BTW, your post does prove my point that rollitup is littered with arrogance. Are you the experiment Nazi? Do I have to get an authorization from you before I continue?

Three strikes and I'm out. Thanks for letting me know, umpire. (sarcasm)

Something else I would like to say. Given this is a website for 18+ we're all adults. I would hope that most adults have enough sense to realize running a 400w for 24 hours would out veg a 250w running for 24 hours.

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I'm just pointing out that your test can't prove anything because you left multiple variables. I could just as validly say that the reason for any difference is the strain as you could that it is the light cycle. I could also just as validly say that the lights were responsible for the difference. I could use any of your variable to claim that is where the difference came from, but with more than 1 variable, you don't actually know what made the difference. That is my only point, sorry I was a dick with the 3 strikes your out comment. Just consider narrowing down the variables on your next experiment, side by sides are the best for this reason.

nomofatum said:

I'm just pointing out that your test can't prove anything because you left multiple variables. I could just as validly say that the reason for any difference is the strain as you could that it is the light cycle. I could also just as validly say that the lights were responsible for the difference. I could use any of your variable to claim that is where the difference came from, but with more than 1 variable, you don't actually know what made the difference. That is my only point, sorry I was a dick with the 3 strikes your out comment. Just consider narrowing down the variables on your next experiment, side by sides are the best for this reason.

Click to expand...

And you definitely make a good point. I was basing my observations on that I have done multiple grows of varying strains with the same 400w MH at 16/8. When it comes to nodular growth they are at about the same, but the genetics definitely show(bushier, shorter, fat/skinny leaves) 20/4 is the only time I've noticed a massive difference in growth speed while vegging.

Plant 1 Day 1


Plant 2 Day 1


Plant 1 Day 5


Plant 2 Day 5


Plant 1 Day 10


Plant 2 Day 10


Plant 1 Day 15


Plant 2 Day 15


Plants 1 & 2 were both grown under 16/8 and a 400w MH. If you count the sets of fan leaves they are the same, yet the shape and look of the leaves are vastly different. RIU won't allow me to upload more images so I'll have to make another post.

Plant #3 was also done under 16/8, Plant #4 is 24/0 and as you can see it's growing at a much faster pace, even though I'm using a lower wattage light(250w CFL)

Plant 3 Day 1


Plant 3 Day 5


Plant 3 Day 10


Plant 3 Day 15


Plant 4 Day 1


Plant 4 Day 5


Plant 4 Day 10


Plant 4 Day 15

mr2shim said:

Plant #3 was also done under 16/8, Plant #4 is 24/0 and as you can see it's growing at a much faster pace, even though I'm using a lower wattage light(250w CFL)

Plant 3 Day 1
View attachment 3353503

Plant 3 Day 5
View attachment 3353504

Plant 3 Day 10
View attachment 3353505

Plant 3 Day 15
View attachment 3353506

Plant 4 Day 1
View attachment 3353508

Plant 4 Day 5
View attachment 3353509

Plant 4 Day 10
View attachment 3353510

Plant 4 Day 15
View attachment 3353511

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so in ur test uve concluded less light grows faster? a cfl out grows the 400 in veg? im confused..

What I'm doing is to see if a lower wattage light running longer would out veg a higher watt light running less. And based on that the answer is yes.

TheChemist77 said:

so in ur test uve concluded less light grows faster? a cfl out grows the 400 in veg? im confused..

What I'm doing is to see if a lower wattage light running longer would out veg a higher watt light running less. And based on that the answer is yes.

Click to expand...

it's not apples to apples on either lights or the plants so there are no fair conclusions to be had here. You are left guessing what variable or variables are responsible for the changes.

TheChemist77 said:

so in ur test uve concluded less light grows faster? a cfl out grows the 400 in veg? im confused.

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I'm not sure where you got "less light grows faster from" Let's apply some basic math here. I'll try to keep it simple.

24 hours of light for 10 days = 240 hours of light. If you're wondering how I got that I took 10 days and multiplied it by how many hours the light is running for. So the equation is 24*10 = 240

16 hours of light for 10 days = 160 hours of light. Again, I got that from multiplying the number of hours the light was on by the number of days it ran for, 10.

So how do you come to the conclusion that I'm saying less light equals more growth?

Maybe you don't understand that plants CAN NOT see lumen as they have no visual perception. Or maybe you don't understand photosynthesis. I figured it wouldn't take a degree in astrophysics to understand the point I was making here, clearly I was mistaken. My bad.

Moving on(hopefully we are understanding now).

Given that every one of the 16/8 plants grew at the same rate(count the nodular growth and take note of the time frame i.e. 5 days, 10 days ect) The 24/0 plant grew at a faster rate(again take note of the nodular growth and time frame relative to that growth and compare it to the 16/8.) You (hopefully) can see the obvious that the 24 hour grew faster. Maybe it was a mistake to compare wattage because a 400w running for 24 hours would grow a plant faster than the same 400w running 16 or 18. But I really didn't think I would have to resort to teaching methods to get the seemingly obvious point across.

In relation to wattage, I'll reiterate that my point was that if we are talking wattage and lamp choice. I would advice anyone looking to veg with a 400w to look at a 250w and run it for 24 hours instead.

mr2shim said:

I'm not sure where you got "less light grows faster from" Let's apply some basic math here. I'll try to keep it simple.

24 hours of light for 10 days = 240 hours of light. If you're wondering how I got that I took 10 days and multiplied it by how many hours the light is running for. So the equation is 24*10 = 240

16 hours of light for 10 days = 160 hours of light. Again, I got that from multiplying the number of hours the light was on by the number of days it ran for, 10.

So how do you come to the conclusion that I'm saying less light equals more growth?

Maybe you don't understand that plants CAN NOT see lumen as they have no visual perception, or maybe you don't understand photosynthesis. I figured it wouldn't take a degree in astrophysics to understand the point I was making here, clearly I was mistaken. My bad.

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They can "see" lumens just fine, well, lumens aren't an actual physical thing, so we can't even see lumens, lol. Plants just don't use exactly the same light wavelengths as our eyes do, so the lumens measure of light output is flawed, a lower lumen count could in theory have higher usable energy umols/par watts, but this is rarely the case and if so the difference is minute.

As lumens increase or decrease umols or par watts increase or decrease at a nearly identical rate. Your plants get half the light energy if they are exposed to half the lumens. Go back to school before you try to educate others.

nomofatum said:

They can "see" lumens just fine, well, lumens aren't an actual physical thing, so we can't even see lumens, lol. Plants just don't use exactly the same light wavelengths as our eyes do, so the lumens measure of light output is flawed, a lower lumen count could in theory have higher usable energy umols/par watts, but this is rarely the case and if so the difference is minute.

As lumens increase or decrease umols or par watts increase or decrease at a nearly identical rate. Your plants get half the light energy if they are exposed to half the lumens. Go back to school before you try to educate others.

Click to expand...

Congratulations at still missing my point, must feel great to be that dense.

ive been growing along time, not an idiot. what i meant was ur test cocluded the plant under cfl for 24 hrs grew faster than pant under 400 watt for 16-18 hrs of light...
in any case, ive done a test comparing male to female ratio under male and female light conditions, male=24/0 female 18/6 along with temp,nutrients, and light spectrum differences..im told seeds are predetermined to be male or female, and that may be the case as even after 100 seeds planted there is no actual proof that conditions determine a plants sex..however i have gotten more females out the female condition room than the male conditioned room..
my conclusion is no matter if i plant 1000 plants i can not prove the conditions dtermine sex. but i think i am proving that as in nature there are more female seeds off a plant than male seeds, as all seeds were off a single plant..just as in nature more females are born every year than men because a single male can impregnate many females..
after 100 seeds regardless of wich room there in i almost always get more females than males..i get a better ratio in the female enviroment, but even in the male enviroment i still get more females than males..

people said the more seeds i plant, at some point it will outcome 50/50..i dont think thats the case..however i cant prove it either way...