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Thread: How many hours of light do I need for veg growth?

  1. #1
    420 Member SmokeyMacPot's Avatar
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    How many hours of light do I need for veg growth?

    18/6 or 24/0, that is the eternal question.

    Those numbers refer to the amount of light and dark that the plant receives (18 hours of light / 6 hours of darkness). Anything above 14 hours of light per day will keep the plant in vegetative mode-- growing leaves and not buds. When you want to switch to flowering you reduce the cycle to 12/12.

    Cannabis plants grow without hassle under 24 hours of continuous light. There has been no controlled recordings of increased hermaphroditism or problems-- most growers now use the full 24/0 cycle.

    However, 18/6 does have it's advantages:

    * Reduced electricity costs. When you have a good mother plant collection and clone cycle, you don't need the increased growth the extra light provides. Lowering the cycle will save money.
    * Allows the equipment and room to cool down. Those 6 hours of darkness can be timed to happen during the hottest part of the day, providing some relief for growers in hot climates.

    Author: administrator

  2. #2
    420 Member QUEENBUD00's Avatar
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    Re: How many hours of light do I need for veg growth?

    I got my girls surrounded by tall bamboo....I put silk flowers 5 or 6 per plant..Im betting they look lovely...from the air...giggle giggle...When the vegetative stage is complete, Im trying out ....to bundle them to switch their modes.... I then untie the bamboo... in a few weeks I notice small buds..now all I do is wait till their plump and oozin' resin...I also talk to them alot,seems to be workin' and I don't feel stupid either,especially when they talk back.....with that stony feelin' .....LATER....
    Last edited by QUEENBUD00; 07-18-2010 at 09:24 AM. Reason: I just noticed that it may be confusing to some readers...I bundle bammboo to let in more light,then untie them to lower the

  3. #3
    420 Member Sensibowl's Avatar
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    Re: How many hours of light do I need for veg growth?

    Quote Originally Posted by QUEENBUD00 View Post
    I got my girls surrounded by tall bamboo....I put silk flowers 5 or 6 per plant..Im betting they look lovely...from the air...giggle giggle...When the vegetative stage is complete, Im trying out ....to bundle them to switch their modes.... I then untie the bamboo... in a few weeks I notice small buds..now all I do is wait till their plump and oozin' resin...I also talk to them alot,seems to be workin' and I don't feel stupid either,especially when they talk back.....with that stony feelin' .....LATER....
    Wow dude. I think you're stoned right now.

    You do know how a forum works, right? You should try to ask questions and give advice, not just talk about how pretty your girls look from the sky. Not really helping anybody with this comment, are you? LOL

    But you don't care, I'm sure.

    Puff puff give...

  4. #4
    420 Member QUEENBUD00's Avatar
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    Re: How many hours of light do I need for veg growth?

    Gee ,sorry dude I was just sayn' i bundle the bamboo to let in more light and untie to force the plants into flowering....silk flowers were for camoflage,and maybe you just get stoned on some of my homegrown huh,?and you feel such like a bongbitch ? what is yur problem buddy ?...Later...

  5. #5
    420 Member Sensibowl's Avatar
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    Re: How many hours of light do I need for veg growth?

    Quote Originally Posted by QUEENBUD00 View Post
    Gee ,sorry dude I was just sayn' i bundle the bamboo to let in more light and untie to force the plants into flowering....silk flowers were for camoflage,and maybe you just get stoned on some of my homegrown huh,?and you feel such like a bongbitch ? what is yur problem buddy ?...Later...
    Dude, I don't get stoned with people who can't write a complete sentence.

    LOL. Chill out. I was just confused by what you wrote, not dogging on you. Try rereading what you wrote, maybe then you can see why others might be confused when you read it.

    (Oh, and this thread is about light not about camouflaging your plants. Might want to go to another thread for that....)


  6. #6
    New Member Hogley's Avatar
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    Re: How many hours of light do I need for veg growth?

    I keep them in 24 hours until first transplant, I then move them to 18/6 until I transplant them again and then move them to 12/12.
    "Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!" - Hunter S. Thompson

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    420 Member WillyBudz's Avatar
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    Re: How many hours of light do I need for veg growth?

    Quote Originally Posted by SmokeyMacPot View Post
    18/6 or 24/0, that is the eternal question.

    Those numbers refer to the amount of light and dark that the plant receives (18 hours of light / 6 hours of darkness). Anything above 14 hours of light per day will keep the plant in vegetative mode-- growing leaves and not buds. When you want to switch to flowering you reduce the cycle to 12/12.

    Cannabis plants grow without hassle under 24 hours of continuous light. There has been no controlled recordings of increased hermaphroditism or problems-- most growers now use the full 24/0 cycle.

    However, 18/6 does have it's advantages:

    * Reduced electricity costs. When you have a good mother plant collection and clone cycle, you don't need the increased growth the extra light provides. Lowering the cycle will save money.
    * Allows the equipment and room to cool down. Those 6 hours of darkness can be timed to happen during the hottest part of the day, providing some relief for growers in hot climates.

    Author: administrator
    I have tried both and see very little difference. I run 20/4 from 4pm till noon. During the winter in Colorado this works well.... helps warm the house at night =)

    WillyB
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    Re: How many hours of light do I need for veg growth?

    I have a friend running 24/24 and I am using 18/6 for vegging. He says he's getting more growth but I heard plants need to sleep. Is this true?

  9. #9
    New Member Jaynseattle's Avatar
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    Re: How many hours of light do I need for veg growth?

    I am a novice, but have talked to a few locals who seem to prefer 14/10 or 16/8 I am personally trying 14/10 atm. But my setup is lacking and doing the best I can with what I have for being a low income MMJ patient.

  10. #10
    420 Member Brett2theMax's Avatar
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    Re: How many hours of light do I need for veg growth?

    14/10 is new to me and if you grow some strains, like G-13, you will run into issues of some plants actually going into flower. I know for a fact that G-13 begins flowering at 14/10, makes a great outdoor strain in northern environments. I've read that 20/4 gives the best results for root development. I have also read that after 16hours of photosynthesis the rate of photosynthesis greatly diminishes, I've been wanting to try 16/4 for a while but I have not bought any digital timers yet. I've read good things about flowering under 16/12 as well, but again have not tried it. There are a lot of different experimental ideas dealing with changing diurnal cycles if you look for it.
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    Re: How many hours of light do I need for veg growth?

    So here is an noon question I have my plants under 12/12 right now and they have been like that for 3 days when will I be able to switch it back to 18/6?

  12. #12
    420 Member burrr's Avatar
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    Re: How many hours of light do I need for veg growth?

    Quote Originally Posted by Mr. President View Post
    So here is an noon question I have my plants under 12/12 right now and they have been like that for 3 days when will I be able to switch it back to 18/6?



    well, do you want them to veg more? or start flowering?
    you can switch it back to 18/6 at exactly 4:20pm Denmark time.

  13. #13
    420 Member HorseBadoritz's Avatar
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    Re: How many hours of light do I need for veg growth?

    Quote Originally Posted by SmokeyMacPot View Post
    18/6 or 24/0, that is the eternal question.
    Hay Smokey,

    Here's some other thinking:

    From Chronic Chrissy

    " Light Cycles

    The dark cycle is very inportant to palnts. Respiration (this is when plants are making energy from sugar to oxygen) Continues in dark but at a much slower pace, almost independent of available oxygen because the leaves are not making oxygen in the dark.

    In the dark there is a shift from leaf production to root production as the leaves transfer excess energy down to the branches and roots. Therefore, some dark time allows for better root structures. The "Experimental Root Growth 10 Days After Cutting" graph on page 33 shows that giving plants a 24-hour light cycle is not the way to supercharge growth"

    This is from "How to supercharge your garden" With the graph on page 33 this follows...

    "Light period for cuttings

    Plants have a free running internal bio-rhythm of 21-27 hours. In this rhythm, they need dark time. Cuttings have a built in daily rhythm (age also) that they inherit from their parent. Cuttings will root better with a 6 hours to 8 hourdark period because this is the main time when leaves and the stems transfer energy down to the root zone for storage and growth."

    The chart has hours of light per day on the bottom, and length of roots in millimeters.
    -@ 4hours of light the roots after ten days were only 22mm long
    -@ 8 hours of light after 10 days the roots were 25 mm long
    -@12 hours of light we shoot up to 40mm long
    -@16 hours it peaks at 50mm
    -@20 hours it drops down to 37mm
    -@ 24 hours it drops down to 29mm

    There is also a shitload of info regarding root to yeild ratio vs veg to yield ratio, and draws the conclusion that at the end of the experiments the root to yield ratio was higher
    __________________ "


  14. #14
    420 Member Brett2theMax's Avatar
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    Re: How many hours of light do I need for veg growth?

    Good info!
    Smoke buds with your buds
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    "Its better to have known puff and to have lost it than to have never puffed at all"
    -Buttercup

  15. #15
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    Re: How many hours of light do I need for veg growth?

    This is my first grow and I'm not sure when to switch to 12/12. Is it by height of the plant or it's age, my plants are 8 wks and about 1' tall.

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