The Dude Grows Show

LED Light Bleaching?

I’ve just recently upgraded from my old HPS to a new dimmable full spectrum LED. In trying to dial in the new lamp height and intensity I may have caused some leaf bleaching. This is a 3×3 closet hydro system night temp 74 F, day temp 82 F, humidity around 50%. PPFD was as high as 1100 but currently around 750 at canopy with no added carbon dioxide. 5 of the 6 plants look pretty healthy except for the light green leaves. The other 1 has normal looking leaves but light green centers. These plants are 2 weeks into flower.

Am I correct, was this caused by the light?

Have I ruined these?


Big Planet


7 responses to “LED Light Bleaching?”

  1. J Mystro Avatar

    It looks like possible light stress. What light do you have and how close to the canopy is/was it? First pic looks bad but second pic looks more like light new growth on the plants with the dark leaves. Interesting genetics to be that dark color so early in flower.

    1. Big Planet Avatar
      Big Planet

      MARS HYDRO FC-E4800 480W
      It was at 32″/75% power. I lowered it down to 16″/75% over a three day period. I think the app controlled timer may have turned up to 100% at some point. When I noticed the lighter color, I raised it to 22″/75%. About 750 ppfd top of canopy. They seem to like it there. This is the third round with the same fertilizer and no other changes except light. Mendobreath all clones from the same mother. The flowers have just started and look good. The dark color was present on previous grows but I’m not sure how early.

      1. J Mystro Avatar

        Light stress tends to be a bit gradual of a fade to start, unless you put them an inch away from the light obviously. Three days isn’t really enough time to cause that lime green color to be so uniform across the leaf. Are you supplementing any calcium? The first pic’s color really looks like calcium antagonism. A lack of nitrogen would be pulled from the bottom, yellowing the lower leaves. Certain trace elements when deficient will fade the top new growth yellow, not lime green. Too much calcium tends to turn the leaves lime green with burnt tips. That’s what I’m seeing. Too much of any one element can wreck the availability of many elements. Remember growing is about balancing many variables. The more light you give them the more food they’ll need and so forth. I think of photons as just another food source to balance in the right ratio. With light, you want to gradually increase the intensity over a week or two. No matter the size. Young plants are far more sensitive than established plants. Start around 500-600 ppfd, then go to 700-800 ppfd after 5-7 days. Then 1000-1100 ppfd after another 5-7 days. If at any time they start to fade up top, back off.

        1. Big Planet Avatar

          If I keep a close eye on the nutrients, do you think I’ll have any trouble later in flower? I’d hate to waste time, energy, and money on something that will never be good.

          Thanks so much for all of the help. It’s greatly appreciated.

  2. Big Planet Avatar

    I always use Canna
    Aqua vega and flora
    Ph down usually
    All at recommended amounts
    No extra calcium
    It may be possible that I had too much fertilizer two weeks before flowering. Could I have caused some kind of lock out?

    1. J Mystro Avatar

      Your nutrient choice should be full proof. Canna is not going to cause an issue with nutrient availability as long as pH is in range. Too much in the right ratio will just cause burn. 1100 ppfd may have just freaked them out. Now that you’ve backed off they should improve.

      1. Big Planet Avatar

        Thanks again
        You rock

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