Reduced hour light cycles

Discussion in 'Advanced Marijuana Cultivation' started by torontoke, Aug 9, 2017.


    torontoke Well-Known Member

    Thanks everyone for chiming in.
    I'm not about to get into an argument over which methods work best and try to blanket statement anything but I'd say the the posts in this thread show how much variance everyone uses to find what works for them.
    I use glr to veg and can't imagine anything causing tighter node spacing.
    I would say that using glr on Indy dom plants have see them mature and even preflower. For satys that could be an advantage to plants that tend to veg out of control. Same way the longer times might be beneficial for someone needing taller plants with stretch and longer distance between nodes.

    rkymtnman Well-Known Member

    yep. it would be basically the same if you tried to grow a plant with a small cfl 5 ft above the plant. it will be very lanky and spindly.
    GroErr likes this.

    rkymtnman Well-Known Member

    i would disagree that the plant can't be growing without light. but i'm not a horti professor. all that i've read is that the cells are elongating during the dark cycle which leads to the stretch. same as when you switch to 12/12 and the plants stretch like crazy.

    i supplement with co2 so it makes more sense for me to run 24/0 anyway.
    churchhaze, GroErr and ttystikk like this.

    rkymtnman Well-Known Member


    ttystikk Well-Known Member

    That blurb said nothing about the how or why, nor did it address timing- which is at the heart of the current debate here.

    Notice that nothing I said above contradicts the article; I was clear that I was talking about short periods of darkness. Until the depletion of the plant's stores of sugars it will indeed continue to grow.

    Beyond that, I'm not at all convinced that the stretch response has much if anything to do with the length of darkness, per se. I think it's a part of the plant switching from vegetative growth to generative (blooming) growth and is an indirect result.

    ttystikk Well-Known Member

    24/0 works best if the light intensity is well below the maximum the plants need.

    rkymtnman Well-Known Member

    here ya go: from Mr Rosenthal
    Need the dark

    By Ed Rosenthal - Thursday, October 23 2003 Tags:
    • <LI class="first taxonomy_term_19">Ask Ed <LI class=taxonomy_term_78>CC44<LI class=taxonomy_term_114>GROWING
    • Lights
    Do plants need a dark period during the vegetative cycle?
    [​IMG]Does marijuana require a dark period during the vegetative growth stage? I recently read a grow book that advocated an 18-6 light cycle during the early growth stages.
    PSD 420,
    One way in which plants are categorized is by the way they gather and handle carbon dioxide. Cannabis is a C3 plant. It uses the CO2 it gathers during the light period, when it is photosynthesizing. Plants designated C4 also gather CO2 during the dark period for use during the light period. Many C3 plants, including cannabis, do not need a rest period. They continue to photosynthesize as long as they are receiving light.
    The plant's photosynthetic rate determines its growth rate because the sugars are used by the plant to build tissue and for energy. Cannabis under continuous light will grow 33% faster than the same plants on an 18-6 light regime.
    GroErr likes this.

    rkymtnman Well-Known Member

    more to peruse:

    "The following information is straight from Greg Green's "The Cannabis Grow Bible"

    Cannabis is a light demanding plant. Professional growers keep the light on their plants using the 24/0 photoperiod for this reason. Plants that grow under 24/0 flourish and do not need a quantity of darkness in order to rest and perform photosynthesis properly. Plants that are grown in optimal conditions under 24/0 light regime grow vigorusly and the benefits of a 24/0 photoperiod can be seen actively in the results. More nodes are formed, more branches are created, leaf numbers increase, the plant is growing at its finest.

    Some growers opt to use 18/6 as their photoperiod. This is 18 hours of light, six hours of darkness light regime. Under these conditions the plant will grow quite naturally but not as vigorously as the 24/0 photoperiod.

    The 18/6 photoperiod expels 3/4 the amount of light that a 24/0 photoperiod does. Although this does not mean that a plant produces 1/4 less leaves,branches and nodes under the 18/6 photoperiod, it certainly does show the correlation between light and cannabis growth. As we have said already, cannabis is a light demanding plant. There are no problems associated with 24/0 and although some have attributed cannabis sexual dysfunction (the hermaphrodite conditon) to 18/6 photoperiod these problems are actually the result of heat stress.

    A 24/0 photoperiod requires that your grow room temperature be kept well monitored. The 18/6 option is cheaper to run. You use a quarter less electricity and this will have an impact on your electricity bill. Also the 18/6 photoperiod will generally extend the bulb's lifespan. During the 6 hours of darkness the grow room is allowed to cool down for this period but a well maintained good grow room setup should not require a cooling down period.

    24/0 and 18/6 both share the same problem though. Once you start the photoperiod you should keep that way especially when the plants near maturity (the preflowering stage). An irregular photoperiod can cause more males than females to develop. It can also cause sexual dysfunction to appear. Whether you choose 24/0 or 18/6 as your vegetative photoperiod try to keep that photoperiod unitl your plants are mature enough to express their se

    churchhaze Well-Known Member

    How about you guys prove your claim that 18/6 can actually save power over 24/0.
    rkymtnman likes this.

    SouthCross Well-Known Member

    When was the grow bible first published? What technology was used to base the information on? How modern were the plants?

    How many revisions has the book gone through?
    SonsOfAvery likes this.

    rkymtnman Well-Known Member

    unknown. grow technology. cannabis has been a plant for many years. 1 revision.

    churchhaze Well-Known Member

    When %Pfr goes down, there's an immediate change in gene expression.
    rkymtnman likes this.

    rkymtnman Well-Known Member

    translate to plain English por favor!

    churchhaze Well-Known Member

    High %Pfr (percent of total phytochromes in Pfr form) means low stretch and while low %Pfr causes exponentially more stretch. (while in veg).

    Pfr will slowly turn to Pr in darkness.
    budman111, SonsOfAvery and rkymtnman like this.

    rkymtnman Well-Known Member

    much better! thanks!! that i understand.

    Jimdamick Well-Known Member

    That's why every day in the morning, I adjust my lights, because most actual growth occurs in the dark period.
    That is my firm belief. (I run 11/13 bloom and 18/6 veg)
    Gaz29, stnr420 and torontoke like this.

    whitebb2727 Well-Known Member

    Everyone quotes the c3 plant thing. That really doesn't mean anything. 85% of all its are c3. The quotes never go beyond saying they are c3 and it deals with the way they use c02.

    Its much more complicated. I won't post anything in particular. Just Google c3 plant and read. Its much more in depth than that.

    I grow numerous house plants under low voltage leds under 24/0. Just like cannabis they handle it just fine.

    Just because they can do it doesn't mean they should. My opinion is they need a rest period. That's just my opinion though.

    ttystikk Well-Known Member

    I think we're splitting hairs here. It's clear they're happy in both regimes.

    Whatever advantage there might be one way or the other is relatively small.

    BobCajun Well-Known Member

    I got better growth with less bleaching after changing from 24/0 to 23/1. I wouldn't go longer than that with the dark though, because they put out too much moisture when respiring in the dark. An hour worked out real nice. Weird nobody tried that before, just 24/0 or 20/4. You'd be surprised how much just an hour off helps reduce light damage. The dark hour seems to revitalize them, probably related to light saturation.

    rkymtnman Well-Known Member

    too each his own. and i don't need a veg timer, so there! lol. grower preference for sure though.

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