Changing light cycle - how to do it best?

Discussion in 'First Time Marijuana Growers' started by vittujoo, May 16, 2010.

  1. I'm facing a problem: temperatures where i live have gone up in the last few weeks alot and my light cycle of 12/12 has been light on during day and light off during night time. now that the temps are up during the day, the temps in my tent are up too much. So i would need to flip thye cycle so that the lights are on during the night and off during the day.

    How should i best go forward with this? Have them on 24hrs continuously or perhaps off for 24 hrs? I'm in third week of flower.
  2. From what I understand, Cannabis keys on the length of night and not the length of day, therefore you should be able to manually give them longer days but maintain the 12 hour nights until you get it where you want it. I think 9PM-9AM for lights on seems to work well for heat control.

    Another option would be to shift it gradually. DJ Short once said that adjustments should be made in 15 minute intervals for optimal health but I have been much more heavy handed than that with no sever problems.

    If you are experiencing very high temps then solving that problem ASAP is the best thing you can do. High temps can cause stretching, fluffy buds, leaf damage and hermies.
  3. oh dear, this is way harder than i thought :D i just thought id give them 24hrs of night and that would be it. i guess im starting today and will give them 2 hours of more light.
    Thanks for your reply. greatly appreciated!
  4. In theory you could just give them a 24 day or however long you need it to be to get you where you want to be. Some growers have fancy timers and will do 16 hour days and 12 hours nights the entire flowering cycle. I'll have to try that one someday!
  5. You can leave the lights on, and then set them to go off when you want you're new light cycle to begin. It won't hurt 'em. We've had to do it a few times and no hermie's or anything here. Just make sure that you don't have any light leaks in your flower area since lights out will be during the day.

    Good luck! :smoke:
  6. im going to go against the grain here and say that you should give your girls an extra night, not an extra day, especially since you are having high temp troubles.

    i wouldnt start adding a couple of hours a night and gradually change over. messing with the light cycle like that during flowering is a good way to get your girls to go hermie. do it all at once. like ripping off a band-aid.

    i hope this helps!
  7. farmer is do this during flowering just keep the light off until you want your desired day time to start..this will not disrupt them what so ever since the night hour's will still be longer than they day...which is what they are used to anyway..and this will help battle that temp..

    dionyoda's method work's as well, but does take a slight chance..but for veg period changes..this would be spot on for sure..

  8. hey bud, your right they do measure night hours for sure:D
    but if you give then more light you cut them night hour's in a 24 hour period...your almost right..just give them night hours instead of day extra..
    you just had it backward's but i can see your learning all the time...;)
    i do this during power out..
    say there in flower and on there day light hour's..power goes out, just leave the light's off at this point..they will still get more night hour's to measure vs day, this still tell's them to flower.. it does not disrupt them at all..
  9. Hey Custom280Z :wave:

    how's it going?

    Thanks for the tip, I'll take all the info from other growers that I can get :smoke:

    Just to clarify, I told the OP lights on, because the one experience I had with lights out for 24 hours - my girls freaked and so did I. They did not look good and it took them a couple days to bounce back from the extended dark period.

    There have been several times that we've given our girls more hours of light then dark during flower and they've been absolutely fine. :)
  10. I could be misunderstanding your interpretation but what I meant to suggest is making a temporary 36 hour long cycle, 24 of light and 12 of dark. I didn't mean to suggest to use a 24 hour timer and shortchange the night cycle.

    On the other hand are you suggesting a 36 hour cycle with 24 dark?

    Possibly it doesn't matter either way, but the reason I suggested not altering the length of the night was based on secondtry's discussion of using 28 hour long days with 16 day and 12 night. There was a list of references to support this but in honesty I didn't read them!

    "Cannabis is a 'long night' plant, so it needs 10-12 hours of darkness to flower, the hours of light doesn't effect flowering, that's the job of darkness. That said, you could change the diurnal hours (length of one day) from 24 hours to 28 hours, that is what I do. I use 16/12 for flowering. For pre-flower I use 8 on/12 off; that limits stretching and helps keep internodes close, it also reduces the pre-flower time from say 14 days to 10-12 days. 8 hours is about as little daylength as is wise.

    For veg I use 16/8. It's best to not exceed 16-17 hours of light a day, 18 hours can be too much in terms of reducing Pn (rate of photosynthesis), carbon assimilation and partition, etc. Running lights at 24/0 will make the Pn drop drastically after the first two-three days or so.

    Supposedly increases yield. Hell I'll have to give that one a try someday and see if it works. He must be growing sativas tho because I tried the 16/8 vegging thing and some ladies started to preflower!
  11. #11 custom280Z, May 16, 2010
    Last edited by a moderator: May 17, 2010
    right..see mj's timer is alway's set in a 24 hour period..;)

    i guess the best way to explain how i do
    doinyoda's way work's well too because it's only 1 day of change..but during flower you really just want to keep more night hour's than day in a 24 hour period..
    you can train them from seeling on a longer photoperiod through lighting techniques, but they all pretty much know 24 hour's and that's it...
    i had a few power outages in a span of one week..this happened at the begining of spring with a flower room full of bud..
    my light's came on at midnight(12am) and power shut off cause the storm around they only got an hour or two of there daylight..
    so i just unplug the light's from the timer..
    leave them off until 12am the next day...
    they never saw a difference...because there dark time was still longer than the light period hour's on that 24 hour cycle..wich is normal for flowering..
    then it happened again like 3 day's i did the same thing again...
    work's everytime...i live in FL so storm's and canes are a pretty common challenge for indoor grower' we do this method to counter it since it happen's all the

  12. wow, interesting..i know if the temp's are quite lower at night than daylight hour's this will cause some shock to them....being in that dark with lower temp's.. how come your light's had to be off for a full 24 hour's?

    i never had one off for the full 24 either
    i just get power out's alot..

  13. Unexpected, nosy house guests that were / are NOT in the "know".

    Budslinger and I talked about this a bit, and he reminded me that:
    When given early in flower, more hours of dark can cause loss of bud mass come harvest time. At the end of flower, a common procedure for ripening bud is to give them more dark, simulating the shortened daylight hours outside. Which is why growers that give more hours of light through the middle of the flower (say 13/11), switch back to a light schedule with more hours of dark closer to harvest (12/12). Just thought I'd share ;)

    In that particular area our temps range within 5 degrees, lights on / off.

    If we got power outages a lot, I would freak out!
    Do you have a generator?

  14. great info! thanx for sharing..
    i guess i just alway's try to stick to the more hour's of dark then light during flowering..
    that is interesting and i've read up a bit on changing light cycles a bit...crazy what you can achieve with research ya?
    don't ya hate unexpected guest!..:smoking:
    it alway's kill's my
    no gen here...we just work around it...alot of folk's i know do..
    they useually get it up and running within 6 hours so it's just a pain to deal with..
  15. To change light cycle timing during veg, extend light or shorten dark, never shorten light.

    To change light cycle timing during flower it's just the opposite, extend dark or shorten light, never shorten dark.

  16. Hi Toasty :wave:

    Would you please explain why you say not to shorten the dark period during flower? Thanks :)
  17. ya that's kinda what i said already
  18. i'm a noob grower my self still but i think the answer is it can cause undue stress and cause hermies and probly a range of other problams that i am my self unaware of lol sorry if i'm not of any help

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