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Thread: 12 hours of light or 12 of hours dark, first.

  1. #1
    PhatJay is offline Registered+
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    12 hours of light or 12 of hours dark, first.

    My 1st grow has finished vegging and is ready to switch to the 12/12 light cycle for flowering. Do I start with 12 hours of light or 12 hours of dark? Does it matter?

  2. #2
    bigtopsfinn's Avatar
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    Doesn't really matter, start with one and stick with the schedule

    I've heard of people starting with 36 hours darkness to induce flowering faster, can't say if it works or not.
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  3. #3
    PhatJay is offline Registered+
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    Thanks for the quick response. I have been looking at the pics of your 1st grow. If mine turn out half as good as that, I will be well chuffed.


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    Ocotillo is offline Registered+
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    Quote Originally Posted by PhatJay View Post
    My 1st grow has finished vegging and is ready to switch to the 12/12 light cycle for flowering. Do I start with 12 hours of light or 12 hours of dark? Does it matter?
    I'm far from an expert, although I've read if you change schedules to always keep your "on" time the same and adjust the end time. I do however believe that really applies to while they are doing the flower power.

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  5. #5
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    Quote Originally Posted by bigtopsfinn View Post
    I've heard of people starting with 36 hours darkness to induce flowering faster, can't say if it works or not.
    I dont know anything about 36 hours of darkness at the start of flowering, maybe its good, again I dont know, but I have heard of and tried whats called "shock treatment" in the latest issue of High Times, which is 3 days or so of darkness just prior to harvest. Supposedly makes the plants get an extra boost in resin, which did seem to take place for me

  6. #6
    PhatJay is offline Registered+
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    Quote Originally Posted by ShittyJon View Post
    I dont know anything about 36 hours of darkness at the start of flowering, maybe its good, again I dont know, but I have heard of and tried whats called "shock treatment" in the latest issue of High Times, which is 3 days or so of darkness just prior to harvest. Supposedly makes the plants get an extra boost in resin, which did seem to take place for me
    I too have read about this "shock treatment" or as some call it "Shock Ripening" and I am planning on trying this out. I have one question about it though. Do you wait till the buds are ready for harvest and then do the shock ripening? Or do you start the shock ripening 3-5 days before you think the buds are ready?

    Sorry for the belated reply, I forgot to subscribe to my own thread.

  7. #7
    thepaan is offline Registered+
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    Flowering is a phytochrome response. Phytochrome exists in two forms which are converted between each other. One form (Pr) is converted by red light (around 660 nm) to the other form (Pfr) which can revert to Pr in the dark or by exposire to far red light (around 730 nm). Using the ratio of Pr to Pfr a plant is able to detect the length of the night and when it is shaded. The night length triggers the flowering response for most plants. Some plants like cannabis will flower regardless, but others have an absolute requirement. Furthermore, some plants (cannabis again) flower when the nights become too long, but others flower when the nights become too short. Once a plant has been indiced to flower it continues to do so due to a chemichal propogated from the leaves. A leaf from a flowering plant can be grafted onto one which has not begun to flower and that plant will subsequently be indiced to flower.

    From this we can reason that yes, a long dark period (maybe 14-16 hrs daily or, I suppose, a 36 hr "shock treatment") can be used to induce flowering in cannabis. Alternatively, you can increase the amount of far red light your plant recieves such that it recieves more than the amount of red.
    Attached Thumbnails Attached Thumbnails 12 hours of light or 12 of hours dark, first.-ft796nb4n2_00082.gif   12 hours of light or 12 of hours dark, first.-phytochrome-destruction.gif  

  8. #8
    stra8outtaWeed's Avatar
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    3 days of darkness at the end!

    from doing this i do notice more swelling with this method. i was told from breeder that this stops the plants intake if nitrogen which will make your end product smoother and tastier along with a little increased weight at finish!

  9. #9
    PhatJay is offline Registered+
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    Quote Originally Posted by thepaan View Post
    Once a plant has been indiced to flower it continues to do so due to a chemichal propogated from the leaves. A leaf from a flowering plant can be grafted onto one which has not begun to flower and that plant will subsequently be indiced to flower.
    That's interesting, if a plant is chemically locked into flowering mode, why is the 12/12 light cycle kept? Just thinking out loud here, but does that mean you could 12/12 for a week to induce flowering and then switch back to 18/6?

    I wish I had more room to experiment with this kind of thing, but I expect someone has already tried it and failed, otherwise we would have heard about it by now.
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    I would advise turning the lights off for 48-72 hours prior to starting the flower cycle. This will shock the plants and jump start the budding process. Also, when you are ready to harvest, I would do the same....it helps push out any last bits of resin.

    Also, you can put plants back into vegetation after flowering cycle has started. I believe it's called secondary budding. I've heard that it can increase your yields by about 25%. Which could be worth it if you aren't worried about time.

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  11. #11
    thepaan is offline Registered+
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    I was thinking more about this lately and it occured to me that 36 hours or a multiple of an entire day plus half would be the best length for an initial dark period. There was a study done on resetting the clock during the dark period (which I can't seem to find at the moment) where they had the most success resetting in a 12:12 light dark cycle at the 6 hour mark. with a 2 hour window. Take this with the fact that the rythm persists (although somewhat diminished) after a full day of darkness, then you have 36 hours as an excellent choice.

  12. #12
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    To answer the first guys question I give them the darkness 3-5 days before harvest. Meaning when I think Im about 3-5 days out I go dark. AK-47 by the way.

  13. #13
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    Cool Weeeeelll.... I know I've always been a maverick...

    ...but after my aforementioned Problems With Exhaust Fans, I kinda left a single 26w/100w Equiv. 2700k Warm White CFL starin' at 'em in their Dark Cycle, initially while they were used to 18 from the HPS above, and then, after a day and a half, the HPS was on for 12h, but the Single CFL persisted. For Three Days.

    I am not sure why I did this. I suppose that I wanted to try the 'other' way of doing things, which was to give 'em a looooonng 'day' that said "LONGEST day of summer @ high latitude, and then when I turned the lights off for 12, well, let's just say that they /slept/...

    Such lovely little (git'n BIG!) girls...
    Attached Thumbnails Attached Thumbnails 12 hours of light or 12 of hours dark, first.-0426000720b-teaser-600x450.jpg   12 hours of light or 12 of hours dark, first.-0505002306-fim2.jpg  
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  14. #14
    shaimeless is offline Registered
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    turn the lights off for 24 -36 hrs then run 12 on then 12 off cycle thats what ive done its very affective

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