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Dropping Temps During Flowering.

Discussion in 'Advanced Marijuana Cultivation' started by ASMALLVOICE, Jan 29, 2013.


    ASMALLVOICE Well-Known Member

    Greetings Fellow Growers,

    I have a question. I have very tight control over the temps in my grow room. I know that when we go to a 12/12 cycle, it imitates the shorter days of fall. I am curious if slowly lowering the temps both during lights on and lights off would have an effect on the final product.

    I have them at 78 during lights on and 68 at lights off. I want to try 74 lights on and 64 lights off and drop each week untill I harvest at 68 on and 58 off. I am starting my 5th week of flowering.

    Just curious if anyone has tried this. Seems to me, it imitates the natural cycle a bit closer.

    Look forward to your input.

    Peace and Great Grows


    elkukupanda Active Member

    Colder temp increase plant phytohormone gibberellin... (Helps breaking dormancy of buds)

    ASMALLVOICE Well-Known Member

    Thank you kindly. I wrote that down and will start doing some research on that, I have not heard that term used before, man, I am such a newb...lol

    Peace and Great Grows

    knotmyself likes this.

    elkukupanda Active Member

    Yes man me too... also some other stuff you can find at UB's thread about carbohydrates and stuff...
    shagalicious likes this.

    Bakatare666 Well-Known Member

    I'm doing 11/13 now, (like short end of season days too) and it's working nice.

    Muffy Active Member

    What is dormancy of buds?

    elkukupanda Active Member

    in other words, stimulates bud development.

    ASMALLVOICE Well-Known Member

    I set it up to drop setpoints by 4 degrees starting Friday lights on at 10:00am. Going to watch it real close for any signs, good or bad. Then next Friday, drop them again. Will throw updates out over the next 3 weeks or so as that should be the 8+ week mark. I have a 40x scope coming in the mail as the 10x jewelers loupe isn't stirring the koolaid for this blind old man..lol I can see the trichs, but I can't REALLY see them.

    Peace and Great Grows


    akula Active Member

    I recently heard about this as well from TheGreenHornet in another thread. I really wanted to look more into this because I accidentally stumbled across it in this winters grow. Trying to save money I turned down my heaters in my flower room just a bit. My temps were hitting 50-60 ranges during the coldest of days. I was worried about them but they seemed to do not only fine, but really thrive. Need to do more investigation.

    elkukupanda Active Member

    Yes, I saw that post and began reading
    Seems like between 2c and 10c have very close results... For gibberellin in some annuals before full winter... I been dropping temp down to 10c and they seem to be liking it... My buds are beginning to form.. But that might be because of the flowering time as well... I been keeping a rotating fan 24/7 on upper canopy to promote as much osmosis as possible during night...

    elkukupanda Active Member


    BCBuddy420 Well-Known Member

    LOVE your thinking!!! :clap: On my first grow I gradually lowered my temps down from 84- 68 to 84-55 and even lower!( I struggled with high temps, they were a lot worse than 84 hehe) my portable AC did this job and I got a good yield with nice purple colors on upper fans and bud leaves ( wasn't a purple strain either). If nature does it then why shouldn't we?? It was ice cold in there for the last two weeks of flowering at dark and they did not show any negative response at all, in any way. I also fed with very cold water too, nothing bad happened.

    bicoastal Member

    What I do that I have found to really bring out all the colors and get the densest possible nugs I follow this regimen;
    9 week cycle

    week 1-6 86 degrees w CO2 78 degrees w/o CO2
    night- 78 degree or 70 degrees

    week 7- 78 degrees w/CO2 75 degrees w/o CO2
    night- 66-68 degrees

    week 8- 73 degrees w/CO2(half level CO2) 70 degrees w/o CO2
    night- 60 degrees

    week 9- 70 degrees no CO2
    night- 55 degrees

    I have found this to work very well for me, what I also have been taught to do is to raise the lights 6 inches once a week for the last two weeks...

    Happy growing!
    knotmyself likes this.

    ASMALLVOICE Well-Known Member

    Many thanx for the replys.

    I have them going to 74 and 64 starting tomorrow and they get a feeding that day as well. Then next Friday 70 and 60-62 and finish with a 68-70 on and 58-60 off. I have kept close to a 10 degree split most of the grow. Did have a spell with a small sensor issue and it ran at about 80-83 (lights on) for about 4 days before my goofy ass caught it, but other than that, been steady.

    I hope I do get to see some color changes. I am starting to see some orange hairs here and there, so I feel pretty comfortable so far.

    Peace and Great Grows


    mushead Active Member

    anyone raise the night time temps? i use to keep mine 80 at night in the summer cuz my days would get warm, then drop them the last few weeks. i was told along time ago that cooler temps made your bud harsher, then again they were super picky stoners.:mrgreen: any thoughts? it was a cali grower that told me that, not sure what that means, just thought it might have been a west coast thing, cuz no one on the east has heard that info that i know of..

    Twitch Well-Known Member

    it will also tun ur buds purple-ish color, the low temps at night
    Rancho Cucamonga

    Rancho Cucamonga Active Member

    Agree with OP.
    Without all the technical and scientific BS I can tell you from experience slowly lowering the temps in flower helps tremendously. The last 4-5 harvests I have started flower at about 79 degrees, down from 82 on the previous ones. Around week 4-6(30 days after signs of first white pistils) I lower day temps to about 75, and around the last two weeks I not only drop temps to about 72 but I crank the dehumidifier up in the next room to get about 30-35% RH. I see nothing but better and bigger yields from controlling the heat in this way.
    I do not switch light schedule at all. From what I have read anything under 12 hours of light will hurt yield. I have experimented with dimming all my 600 watts to 400 the last few weeks but no real results.
    If you look at the life of a marijuana plant in nature seedlings usually have to deal with fairly cooler weather early on, veg is mostly the hot months as is early flower. But there is no question that in late flower temperatures are usually the coolest time of this plants life so it stands to reason cooling in late flower would help with indoor growing as well.
    knotmyself likes this.

    ASMALLVOICE Well-Known Member

    Morning All,

    So far so good for the first step down, have it set for 72 lights on and 62 off, going to be a chilly work week for the Ladies. :twisted: Had to do a bit more staking and supporting, getting some plant matter on the ends of these sticks...lol The last 2 pics are one of the freebies and I have no idea what they are, but I can say this, from a looks standpoint, these two Ladies here just got it going on. I love the frost and the overall symmetry of the plants ( they are a bit younger at just nearly 4 weeks into flower).
    100313.jpg P1010005.jpg P1010007.jpg P1010011.jpg P1010015.jpg 030613.jpg 040613.jpg 090613.jpg P1010012.jpg

    Will throw another update out next week.

    Peace and Great Grows

    Sincerely420 likes this.

    zack66 Well-Known Member

    Looking good man! Those buds look tasty.
    Guitar Man

    Guitar Man Well-Known Member

    I'm enjoying this Thread, as I have been very curious about temps during flowering. Makes total sense to lower temps as the grow matures.

    I do have a question about your grow; I'm not trying to be critical, but your leaves seem to be showing nute problems earlier than they should be. How far into flowering are you?

    Here is a picture of 1 of my plants that was 6 weeks into flowering. I do have some leaves turing color, but lots of green still left.
    . 100_3247.jpg

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