vegetative non 24 hour lighting schedule

Discussion in 'Grow Room Design/Setup' started by canadabus, Jun 18, 2015.

  1. Ive been looking into the effects of different day:night ratios on vegetative plant growth and have seen numbers ranging from 18:6 to 24:0. Naturally one would assume that more light = more photsynthesis = a faster metabolic rate, however 24 hours of light seems... well, unnatural. Surely there is something to be gained from having a period of darkness? To complicate things people on the forums swear both ways.

    Someone in another forum offered up this explaination. The purpose of photosythesis is to create energy in the form of carbohydrates, which is used to fuel plant growth and ultimatly reproduce (to flower). The leaves will retain the carbohydrates during the course of the day before the carbs are pulled down into the roots during the night. The problem is that the leaves are only capable of storing so much carbohydrates, so the effectiveness of a prolonged day cycle is limited. I believe this effect can be at least somewhat negated by the increased photosythesis cause by 24 hour lighting, explaining the mixed views.

    So here is my thoughts. So if we assume 18 hours on as this seems to be the tried and true intervel of daylight, and allow for maybe 2 off just to flush the leaves, perhaps the plants would be able more efficiently metabolize its carbohydrates, speeding growth. Anyway just wanted to see what you guyz thought
  2. i've used both with perfectly fine results
    18/6 helps keep temps stable, if that's an issue, and 24/0 will give you the fastest growth in optimal conditions
  3. I figured both these values could work, but I guess the question is whether or not a cannabis plant would respond positively to a schedule that does not follow the natural 24hour/ day night cycle? My theory is that the 6 hours of night in an 18:6 is redundant and can be reduced to 2 hours, potentially boosting growrates by as much as 17% (theoretically)

    Another possible application could be in flowering. Maybe an 11:11 or 10:10. As far as I know when flowering cannabis is really keen on keeping at least a a 12:12 clock cycle, but whether that is dependent on daynight ratio, or intervels length of dark period idk because everyone uses a 24hour day. Just food for thought.
  4. #4 BrassNwood, Jun 18, 2015
    Last edited by a moderator: Jun 18, 2015
    My 2 cents is that plants are marvelous things they take a bit from the soil and a bit from the air and turn sunlight into cell structure.. Sunlight is the key.. I've vegged under all and use 24-0 as that is fastest IME..
      Flowering is not 12-12.. At least not to the plants.. 14.5 is the actual trigger point for most strains.. At 15 they veg.. At 14 they flower.. Since all my flowering is outside I have no way to test if 14 hours will produce bigger buds in the same length of time but that is my guess.. Buds are still the plant using sunlight to produce plant mass and I'd think the closer you can run to 14.5 without triggering your selected strain back to veg the better.. Ignoring power consumption for bud production.. Just conjecture on my part and someone should put it to the test..

    This covers the Pr and the Pfr and what is making the plant flower.. I shall pose this question to another long term inside grower..
  5. Great resource thanks!
    Unfortunately im not in a position currently to grow so I cant test any of my theories :( I would love to see what your friend has to say and invite anyone reading this to employ this method, if only for scientific purposes.

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