Strangely yellowing leaves at top

Discussion in 'Sick Plants and Problems' started by blood_on_snow, Aug 28, 2007.

  1. Can anyone tell me what this is? it's right at the top which is the part thats getting all the light, the other plants getting the same treatment but nothings happening to it. The leaves are a dark green and the middle and tips are yellow with a clear line distinguishing the two parts.

    I'm using flora nutes with the lucas formula in a soil grow. I know the lucas formula is intended for hydro grows but I thought it would still be fine with a soil grow.

    Their under a 250w HPS and I know their really close to the light but with that fan there they dont burn. The plant furthest from the fan gets some leaf curling towards the top but thats as bad as it gets.

    It doesnt look like anything crucial but it's something new I've come across. Any information would be appreciated. I dont know if it's the light or the nutes... hell maybe it's natural though I doubt it.
     

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  2. I think you are experiencing the same problem I just fixed (the yellowing leaves at the top) it's most likely heat from the lights but it could be a phosphorous deficiency as well.

    Just saw the pictures- it's most likely the light from what that shows. Phosphorous deficiency shows around the edges of the middle of the leaf instead of at the tip- tip burns are from over feeding or light burn.

    Try taking the light up a bit and see what happens, what strength are you feeding at in EC?
     
  3. IMO&exp it's light burn.

    Good advice Mr GoodStuff;)

    Nice to meet ya.

    gl alex
     
  4. Looks like you have the claw in the back ground.
     
  5. GoodStuff- Yeah your probably right about the light. haha now my problem is that I cant raise the light anymore..... I'll fix it somehow. I wouldnt know if it's a Phosphorus problem though since I dont have a meter. I guess I need to put that on my shopping list for my cab.

    420freedme- Thanks for the second opinion, but who's alex?

    swa_swa- What on earth are you talking about? lol
     
  6. Sorry Blood on snow, I forgot my ....alex.

    I'm alex, and gl.
     
  7. Yeah, it really looks like a Phosphorous problem. If it were a heat issue, you'd probably see most of your leaves pointing upward, folding in the middle, and singed tips.

    Could be either one. I'm not a pro, though.
     
  8. I could always try both. I'm fixing the light right now and I could always add potash or something else in when I add ferts next time. From the sick plant guide that I read though it looks like what they called "light bleaching".

    What I think my problem is is not heat stress but light stress. The area at the top of the plant is exceeding 75w psf so the chlorophyll cannot absorb all of the light and it makes like a car engine on jet fuel.

    CannaStats says "Cannabis is a hardy full sun plant that can tolerate a lot more than it can use, we know it can tolerate up to 10,000 fc at the top of its canopy in the sweet spot, but we also know there will be less light reaching beneath the top."

    It also says that a 250 watt HPS light will reach 9,000 fc at 0.58 foot (7 inches/18 cm). 7 inches is a lot further away than the top of my plants are from the light. I estimate that the light intensity where the leaves are yellowing must be beyond 10k fc.

    Anyway like I said we could always try both.

    Thanks guys, lol thanks Alex I'll need it.
     

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