18 hour or 24 hour?

I have grown my plants under 24 hours of lighting since they sprouted (24 days old). I would like to know any pros and cons, advantages or disadvantages, to growing under 24 hours of lighting and 18 hours of lighting.

I have a 150Watt Hps light....

greenearth5 said:

I have grown my plants under 24 hours of lighting since they sprouted (24 days old). I would like to know any pros and cons, advantages or disadvantages, to growing under 24 hours of lighting and 18 hours of lighting.

I have a 150Watt Hps light....

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People say 24/0 promotes hermies so 18/6 is better.

Other people say fuck that, 24/0 is better because you plant grows faster.


18/6 is probably the more ideal way to grow your plant. BTW my first grow was 24/0 for all of vegging. It turned out fantastic, my current grow is using 18/6 and it looks fantastic. Not that questions like this are bad im not saying that, i used to ask them too but after getting all of them answer i realized it doesn't matter. Your just gunna get two people argueing over which one is better without any scientific proof.
Not tryna sound like a dick but just letting you know.

my medical marijuana growers bible says fewer hours of light promotes females they suggest 14d 10 night after the 3rd set of leaves are present..i guess you could give it 24 hours until then.. i go with 18/6 myself but this is only my first try so i dont really no!!

I was thinking that the plants might not be as stressed if they can have a little shut eye...

I have heard that 20/4 is the optimum veg timing schedule, with regards to end yield. Here is post written by OT1 on the subject:

Originally Posted by oldtimer1

We did a lot of experiments with light times a few years back using known sat and sat dom clone lines.

With Vegging ie under hid lights.

20/4 produced the most sturdy growth and the most bulk. Best final yield, taken as 100%.
22/2 Less of both. yield 88%
18/6 Studier than 22/2 but slightly less bulk. yield 87%
24/0 Much lighter in all aspects than 18/6. Yield 79%
16/8 The weediest plants. yield 67%

Plants vegged to final pots under fluorescents at 20w per sq ft on 18/6 yield 49%

Have not tried 36 hrs dark but did try 48 hrs from 18/6 veg. The final yield was down between 15 and 20% by var the pure sats the biggest loss in final weight and caused the odd herm, [sats] it did reduce the flowering time by 5 to 8 days.

For the mum lines we have 20/4 to 12/12 gives the best crop weight and bud quality, really thats all I’m interested in.

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Taken from here.

nocturn3 ..... plus reps for you bro

theplantkiller420 said:

my medical marijuana growers bible says fewer hours of light promotes females they suggest 14d 10 night after the 3rd set of leaves are present

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Don't do this. Some strains can be induced to flower with only 10 hours darkness.

more dark = lower power bill

if i was running a 1000W HPS light then ide worry more about my power bill.. but for my 150W HPS Im not to worried about that...

Thanks thou mate

The advantages of 24/0 are rapid growth and the diadvantages outway the advatages. First, your more likley to get hermies or males, also the roots don't develope as fast as the canopy.

18/6 is ideal they say most likley you will get fem and canopy and roots are equal. Also you say a little electricity with 18/6

based on my research it's a toss up and comes down to grower's preference and what they dial in with their particular strain. There has been no proof given that one is generally than the other.

well.. its a toss up.. i hear that i should stay with the 24/0 and then i hear that i can get hermies that way... i only have 3 plants and i have no more seeds or even hook ups... i also hear that i can get more bud this way

i hear that 18/6 stalls the growth of a plant but it seems like most people use it despite it not giving as much bud

thats where I would start hunting if you are that interested in it. I'm intersted in learning about these things. Haven't quite gotten time to do the undercover stuff. That is way down the road. But go to library and get books on plants. not just pot. See how a plant works. What it does during the day, and what it does during the night. Knowing that I'm sure you can arrive at reasons to do one over the other.

I go with 20 on, 4 off, based mainly on the findings from OT1 which I posted. He knows his shit pretty well, and has been growing longer than many of us have been alive.

There was also a post a couple of weeks ago which backed up the 4 hour dark period as being optimal, based on some scientific stuff about gasses being exchanged at night. I can't seem to find it now, but it had me convinced.

I think im going to go with the 20 on and 4 off mode ..... after a little more research

Do i simply kill my lights for 4 hours a night? or do i need to kill one hour a night and work my way up to 4 hours?

You'll be fine just killing your lights for that time period. There is no real need to do it gradually.

plus reps to flamdrags420 because he seems like an intellectual pot head

I ran 24/0 through veg with clones and had no problems. The buds turned out dense but I had nice short squat plants( on purpose however) Im trying 20/4 as of today however, ill definatly chime back if you screw my plants up check out my last grow in my sig, turned out great

greenearth5 said:

plus reps to flamdrags420 because he seems like an intellectual pot head

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nah just average, or above average. Well, I would like to think I'm smarter than what might seem to be the average teeny bopper stoner.

you seem to take a educational approach to problem solving... i always like having a intelligent conversation...

I set my light to go out at 2am and back on at 6am ..........