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Nitrogen toxicity?

brown_thumb

Active member
I'm not trying to hijack this thread but... my girls have ultra-dark green leaves but no clawing... though they may not be growing as fast as they should. I guess I push the nitrogen a bit hard but it doesn't seem to hurt them. I think it's the extreme heat slowing growth (south Texas outside grow), not excess N. So I guess I don't understand the concern about dark leaves other than too much N seems to be detrimental in mid-late flowering. But I'm a newb with mostly poor results so everyone should take this post with some skepticism.

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I'm not trying to hijack this thread but... my girls have ultra-dark green leaves but no clawing... though they may not be growing as fast as they should. I guess I push the nitrogen a bit hard but it doesn't seem to hurt them. I think it's the extreme heat slowing growth (south Texas outside grow), not excess N. So I guess I don't understand the concern about dark leaves other than too much N seems to be detrimental in mid-late flowering. But I'm a newb with mostly poor results so everyone should take this post with some skepticism.


Those aren't overdosing on N, they're deficient in P. That's why you get the upward curling of the leaf margins without downward clawing at the tips. And of course the dark green color and stunted look. Pretty soon the tips of the older leaves may start to burn and the petioles will turn purple or red. Could be a lockout if you're really pushing the N in your mix. Back off the feeding for a few days and go with a more even NPK mix. Vegging plants need P and K too!
 

brown_thumb

Active member
Those aren't overdosing on N, they're deficient in P. That's why you get the upward curling of the leaf margins without downward clawing at the tips. And of course the dark green color and stunted look. Pretty soon the tips of the older leaves may start to burn and the petioles will turn purple or red. Could be a lockout if you're really pushing the N in your mix. Back off the feeding for a few days and go with a more even NPK mix. Vegging plants need P and K too!

Thank you. I've already begun decreasing N and increasing P/K.
 

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