Light penetration vs temps?

Discussion in 'Growing Marijuana Indoors' started by FarmerJames, Dec 11, 2013.

  1. Hello All,
     
    I have a question regarding light penetration vs surface temps. I keep an IR thermometer in my flower space to monitor the surface temps of the canopy & cola's. On my current bunch that are nearing harvest most of the bud sites are getting so heavy that I have had to tie or prop them up. This has resulted in most the bud sites moving away from the light. The exception is one (quite large) central cola. That one has shot straight up to the light. Kind of caught me by surprise. I tried training it to the side but didn't get very far as the stem is quite rigid.
     
    I dropped the light a bit to try and make sure I was getting enough light in lower portions of the plants. Today it got a bit warmer than it has been (thank God) and I did my daily checks and found the surface temps on the monster bud to be 91-92F. Air temps are 78-80.
     
    Question: Would you raise the light to accommodate the one (large) cola at the expense of the lower/smaller buds or leave the light low and chance affecting the large cola in order to insure good light to lower portions of the plant??
     
    Thanks
     
    FJ

     
  2. nah you should be fine. or you could raise the lights, harvest the giant cola, then move lights down and harvest smaller flowers later. depends on how far into flowering you are
     
  3.  
    I am about a week from harvest at this point. I don't think I am going to make a huge difference on this bunch. I have had this come up in the past and catered to the highest portion of the canopy. It is a bit of a fine line... Not enough light=small buds. Too much heat=airy buds.
     
  4. yeah, well that's what I'm saying. is if you harvest the large cola at your regular date, chances are the smaller buds on the bottom wont be quite as far along and you could leave them in there for another week til they mature enough. Or harvest all at once and make some hash or budder :)
     
  5.  
    I understand your thought. However, I think the lower buds would lose on the opportunity to develop to their full potential if you wait to lower the light until after harvesting the main cola.
     
    I have another bunch that I am working on and attempting to keep the canopy more even by supercropping the taller plants. That will resolve the issue (I hope..) in that bunch.
     
    The ones I am asking about kind of snuck up on me. The plants were of similar height until I quit paying attention for a bit and a couple of them shot up above all of the others. Hopefully I will not see this again but I want to have an informed plan if I do.
     
    Thanks for your input. It is of great value to have folks willing to share on this site.
     
    FJ.
     
  6.  
    I have question kinda regarding this statement. Is light bleaching bad for a plant? I have a 600W light sitting about a foot to 16 inches from the colas and all the tallest ones, especially in the center have essentially started to turn white. Now I don't have any heat issues, I have 3 fans on the plant and my exhaust fan can replace all the air in the grow area about 4-6 times a minute. My temps never go above 80F at the top of the canopy, res temps hover at 65-66. So if you have so much light the leaves turn white, yet the temps stay low, is it positive, negative, or does it not really matter?
     
    Thanks
     
  7. negative. that white is essentially the plant leaf losing chlorophyll so that's a lot of the top of the plant that's not photosynthesizing. plants cant grow without photosynthesis :ey:
     
    just raise that light a little. If you can, take the light out of the tent, and take it into a dark room. With the lights in the room off, turn on your light with the reflector or cool tube whatever you have in your grow room. Measure the height at which the light covers the area you are trying to grow in your room and that's how far you should have your light from the canopy.
     
    I know that may not be the easiest to understand so let me use an example to clarify.
     
    Lets say when you hold your light+reflector at 20 inches above the ground, the light covers roughly 3 meters squared. When you hold it at 10 inches off the ground it covers roughly 1 meter squared. Lets say at 15 inches off the ground it covers 2 meters squared. Your plant is about 2 meters squared so you want to keep the light suspended at 15 inches above the canopy. adjust ventilation as needed. this will allow you to utilize every watt of your light in the best way possible. now, these numbers are not factual, just some random numbers I threw out there. you'll have to test yourself to see how your setup performs.
     
    when you hold your light in the dark room it may not be easiest to see how much of a footprint it has....you'll be able to tell a little bit though there should be some sort of a distinct line showing where the reflected light really starts to decline. this image illustrates it well:
     
    [​IMG]
     
  8. Thanks for that explanation. The problem is my light hood is built into and is a part of the box. There is no way to raise the light or lower the plant. Guess I'll just have to ride out this grow and maybe get a smaller bulb in there for future grows.
     
  9.  
    Just a thought: Shorten your veg time to keep the plant(s)  smaller.
     

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