24/0 vs. 18/6 debate is over!!!!

Discussion in 'General Marijuana Growing' started by mafuki, Jan 15, 2010.


    mafuki Active Member

    :bigjoint:"Most green plants are classified as either C3 or C4 which represents how carbon(C) is used during photosynthesis.

    C4 plants temporarily store carbon dioxide(CO2) over the dark period to use for photosynthesis during the day. C4 plants slow down photosynthesis once the stored CO2 is used up and they need to gather it from the air. Which is why trees slow down photosynthesis in the afternoon even though the sun is still bright. This does NOT apply to cannabis.

    C3 plants(:leaf:cannabis/veggies) gather CO2 only during the light period when they are photosynthesizing. During the dark period these plants only use oxygen for their metabolic life processes. They don't uptake CO2, nor do they use it. As soon and as long as the light is on, C3 plants gather and use CO2 for photosynthesis.

    C3 plants also have the ability to use higher concentrations of CO2 than what is found in the air. If the light is bright enough and the plants have sufficient nutes, their growth rate will accelerate from it(2000ppm vs. 400ppm of CO2), which increases yield. They can do this continuously, without a dark period throughout the vegetative stage.

    The dark reaction is a process of photosynthesis that takes place in both darkness and light. It uses ATP and NADPH molecules that hold energy absorbed from light to break apart CO2 into it's base components.

    Again people get anthropomorphic with their plant needs. People need rest, so plants must too. This is false as well. Light means growth. Scientifically. Although 18/6 will shock your plants less when you switch to 12/12, it's a personal choice whether you would rather sacrifice a little growth for a quicker adjustment or less photo confusion. If you want to save money or energy that's a personal choice too. Do what you need to do to make your growing scenario work.

    Another factor to consider, your ballast/starter life will be shorter the more you turn it on and off."

    Hope this helps.:bigjoint:

    doc111 Well-Known Member

    Ballasts and shit benefit from a rest period and going 18/6 can save quite a bit of $$ over the long run with very little loss in growth.
    Mr.Goodtimes and Carl Spackler like this.

    chitownsmoking Guest

    i have done both and both work fine. ive even gone str8 24 before untill 12/12 it was all good.

    formlessqarrior Member

    +rep but what u mean the debate is over so 18/6 for sure is what it seems you are implying

    Uk.Cobra Active Member

    i use 20/4 works good for me
    Medicationist likes this.

    daleh717 Well-Known Member

    time to burn one .......................ahhhhhhhhhhhhhhhhhhhhhhhhhhh
    haight and mrgemstone1 like this.

    PeachOibleBoiblePeach#1 Well-Known Member

    This last time I used 24 under cool whites, I noticed it was not doing it?? I than switched to 18/6 they started to do it?? Now I got them under 400 MH/conversion bulb and the are surely doing it.
    INMO, 18/6 is where it's at. But I can read and feel my plant's needs.
    morgwar likes this.

    seasmoke Active Member

    i agree with these guys. alot can be saved not using elec for 6 hours....I currently have been running 24-0, but will switch to 18-6.

    I do like the theory though...

    doc111 Well-Known Member


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    mygirls Medical Marijuana (MOD)

    i have done both and prefer 18/6 after trying 24/0. plant root growth when light are off and it all starts with a good root mass to grow a good plant. :bigjoint: and personaly i see a better grow spurt running 18/6
    3eyes and Medicationist like this.
    CaNNaBiZ CaNucK

    CaNNaBiZ CaNucK Well-Known Member

    I'd love to agree with you (God knows I would) but this debate will NEVER end. Both work and both have benefits.

    And really, threads like this are staples in our forums. "MH vs. HPS for flower", Flush vs. no Flush" etc. So like the greatest debate of them all, Creation vs. Evolution, these ones will continue to spark conversation and innovative ideas till the end of time.

    I, for one, welcome them :bigjoint:

    GanjaClimber Member

    I am noob on my first grow but I have a healthy strain (l.a. woman) so I'd like to play with a the lights little bit and see what results I can get.

    I began at 21/ 3
    I plan on switching to 5:30/ 18:30 soon for the remainder of veg :?:

    For flower at first, I plan on going to 12/ 12 for the first 5 or maybe even 6 weeks. I will see how she's doing.
    Then I'd like to drop the light even more like 10/ 14 and even if it takes an additional few days or week for her to finish, I have heard this can increase potency. Is this true?

    mafuki Active Member

    Yes my point was that the process that happens during dark hours for class C3 plants(Cannabis) also happens during light hours so really the only thing that technically changes during the night is that the process of photosynthesis stops and the plants grow taller in search of light. The Calvin cycle which most people refer to as the "dark stage" happens during the light stage in the same amount as it does during the dark stage in Weed(class C3) so Scientifically Marijuana does not need the dark and will "yield" more as long as there is sufficient H20 and food to accommodate the photosynthesis during the long light hours. class C4 plants are like humans in which they need rest but class C3 plants(Cannabis) do not. They will thrive as long as they get light, food, water etc. They will not get tired and need to sleep or rest. The only thing the dark time will do is stretch the plant and stop it from photosynthesizing and gathering of C02.

    Stick with 24/0 your plant will thank you. It will be more compact with stocky buds and less node spacing.
    HighNickin420 and Mr.GreenJeans like this.

    HomeGrown420baby Well-Known Member

    i noticed my plants get bushier when i veg 24/0..now i start at 24/0 for a week from clone then 22/2 for a few days then 20/4 till their as big as i want em to be and then i flower

    Acuity Active Member

    It has been known for ages that Cannabis is a C3 plant.

    Cannabis benefits from "a" dark period in any 24 hours far above these silly photosynthetic carbon fixation arguments always rests on.

    I run 20/4 personally, I would never run 24/0 despite knowing they would grow faster because plant development is not all about growth rates...

    I have an MSc in plant sciences and know what I am talking about if anyone cares.

    Those who want to know more can google things like

    "Cirrcadian rhythm, phytochrome, photomorphogenesis, chloroplast physiology, brassinosteroids".
    vostok, Mamba01 and sicks stuff like this.

    Wetdog Well-Known Member

    No, it is not true.

    Ref Rob Clarke's "Marijuana Botany", 10 hrs light, DECREASED potency. You heard wrong bubba, but try it if you like.:wall:

    Do some research instead of listening to internet bullshit.

    haight likes this.

    HomeGrown420baby Well-Known Member

    i get more of a stretch to my plants when i dont go 24/0

    sherriberry New Member

    18 and 6 makes more seedlings female and gives less chance of a hermie, so thats a serious perk.
    TheChemist77 likes this.

    MacGuyver4.2.0 Well-Known Member

    Another secret to 18/6 is temperature. If you run lights for 18 hrs at a comfy 75 degrees F and then the lights go out and temp drops alot, that slows plant growth down. Starches, sugars and other elements all metabolize at different temps. Water is even absorbed by roots better at a tepid temperature (not too warm, not too cold). Firm believer in 18/6 for alot of the reasons already discussed in this thread. :)
    Mamba01 and haight like this.

    mafuki Active Member

    I was implying that besides the electric bill and ballast cooling which 18/6 is better for that 24/0 IMO is the best and will give the plant continuous growth and does not need darkness to "rest/rebuild or whatever the myth is" The process which occurs during the night also occurs during the day with the same amount of effect(FOR CLASS C3 PLANTS I.E. CANNABIS) but is not collecting C02 during the dark which it uses for Photosynthesis during the light so if you have 2 processes working during the light and only 1 working during the dark then wouldn't it be logical to choose the period which has the most processes occurring?:lol:
    Michael Huntherz likes this.

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