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How much LED light can a plant handle?

Discussion in 'Indoor Growing' started by Lite, Nov 6, 2017.

  1.  
    Humanrob

    Humanrob Well-Known Member

    @Lite - what size is the tent? and how close are the lights to the top of the plant?
     
  2.  
    Lite

    Lite Well-Known Member

    3x3 tent, 18-24" above canopy
     
    Humanrob likes this.
  3.  
    Humanrob

    Humanrob Well-Known Member

    So at "1148 True watts" you are running at about 127.5 watts per square foot.

    Wow.
     
    GreenLogician and Rolla J like this.
  4.  
    Humanrob

    Humanrob Well-Known Member

    Is this the same plant that is in your grow journal? How long did you veg for?
     
  5.  
    Ryante55

    Ryante55 Well-Known Member

    I run 750w of qb at 700ma over a 4x4 plants are about 16 inches away with no problems I'll put the light a couple feet away when I first plant the clones but that's more to add a little stretch so I can lollipop. I'm guessing you need over 50w/sqft to cause any issues
     
    GreenLogician and verticalgrow like this.
  6.  
    CannaBruh

    CannaBruh Well-Known Member

    the point to take home is i get much much better results at 20W/sqft than i was getting with 60W/sqft
     
    GreenLogician and Humanrob like this.
  7.  
    Lite

    Lite Well-Known Member

    7 weeks, yes it is. i reduced down to 855watts due to canoeing and one lights fans breaking. I guess the answer is, in a 3x3 tent, dont exceed > 1000 true watts of LED. The fans couldnt stop the extremely low humidity caused by that much light.
     
    Last edited: Nov 12, 2017
    Possum1 and Humanrob like this.
  8.  
    Humanrob

    Humanrob Well-Known Member

    Based on the massive trunk on that thing I would have guessed 9 weeks, but some plants grow faster than others. With light there is a point of diminishing returns, and then there is a point where it becomes detrimental. You have mentioned two goals (I'm paraphrasing but hopefully not misunderstanding): (a) to see how much light the plant can take, and (b) to try and get 1+ lbs from the grow. The answer to A might undermine the answer to B. In other words, how much light you can give it without killing it might give you a stressed plant that yields much less than a plant with an optimal amount of light. I don't know much about red/blue LEDs, and I don't recall reading how much light will give you the healthiest happiest plant possible, but it looks like you'll find out. With COBs, there seem to be a lot more people on RIU are testing and sharing their information, and depending on your feeding style between 37.5w and 50w per square foot is a safe and happy range.

    Keep that plant happy and I'm sure you'll pull a pound no problem.
     
    GreenLogician and coreywebster like this.
  9.  
    mr sunshine

    mr sunshine Well-Known Member

    Light burn sets in when the lights are to close to the canopy.
     
  10.  
    Lite

    Lite Well-Known Member

    they were nt getting light burn but they were getting low humidity stress due to the actual radiation on the leaves. and @Humanrob I did start this as a clone, which makes up for ur missing 2 weeks :)
     
    Humanrob likes this.
  11.  
    Shawndeadhead

    Shawndeadhead Active Member

    Yep yep yep 500W DIY led cobs over 4x4 2lb
    1000w hps over same 4x4 same strains 1.25 to maybe 1.5 lb best.
     
  12.  
    GreenLogician

    GreenLogician Well-Known Member

    I seem to burn my plants with cobs real easy. But maybe I'm just not keeping up with the nutes?
    I've got six cxb3950s in a 80x80cm, and I get my leaves yellowing off if I run them much above 250w.
    It's been recommended to me that I need to keep my temps right up?
     
  13.  
    Lite

    Lite Well-Known Member

    No clue. I just feed when I see it needs it, and cut back when I see burning
     
  14.  
    coreywebster

    coreywebster Well-Known Member

    With or without reflectors/lenses ?
     
  15.  
    CannaBruh

    CannaBruh Well-Known Member

    You're frying them... try running each of those COBS at 10-20W
     
  16.  
    GreenLogician

    GreenLogician Well-Known Member

    120 degree lenses.


    That's what it feels like! Why is it like that for COBS, when people like the OP can go cray cray with the blurples?
    Maybe plants are more easily stressed by high levels of green, or something not in the blurps?
     
  17.  
    Yodaweed

    Yodaweed Well-Known Member

    I'd suggest using a 315 cmh, you could get some really good light coverage from a single cmh in that sized area and the quality of spectrum is much better than those LEDs.
     
    coreywebster likes this.
  18.  
    coreywebster

    coreywebster Well-Known Member

    Blurples don't put out the photons cobs do. But ive seen really bleached buds from blurple. My cobs don't bleach anything 6" from main colas. But I run with no reflectors or lens. I have not seen a proper cob bleach a bud site on anyones grows yet.
    My QBs can give light burn to fans if I'm not careful, not surprising though, they give solid buds 3 feet down. My cobs don't penetrate that far, but like I say lack of lens means more light spread out, not so many hotspots.

    I think I would just raise my light if possible rather than dim, get them beams blending better.
     
    Last edited: Nov 13, 2017
    GreenLogician likes this.
  19.  
    CannaBruh

    CannaBruh Well-Known Member

    I've seen tons of bleaching from cobs, and it's almost always the temps are getting too hot for how close how hard we are running the COBS. Dial back the wattage or cool the room some and the bleaching should improve.
     
    coreywebster likes this.
  20.  
    Michiganjesse

    Michiganjesse Well-Known Member

    mauricem00 likes this.

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