Clawing Leaves: The Nitrogen Toxicity Signature
The claw is a leaf whose tip curls sharply downward while the rest stays flat, often with an unnaturally dark, glossy green color. It is a warning that arrives before nutrient burn.
Nitrogen toxicity
Overfeeding nitrogen, especially by continuing a veg feed into flower, produces dark glossy leaves with clawed tips. Reduce feed strength and shift to a bloom ratio.
Other causes
Overwatering causes a softer, whole-leaf downward curl rather than a sharp tip claw. Root problems and heat stress can also produce claw-like curling, usually alongside other symptoms.
What to do
Cut nutrient strength by a third, verify pH, and give a plain pH'd watering. If runoff ppm is well above input, flush. Judge results on new growth over the next week.
Frequently asked questions
- Is a slight claw dangerous?
- Not immediately, but it means you are at the top of the plant's tolerance and burn is next.
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