Health Library

Nitrogen toxicity is one of the most common cannabis problems, and it's almost always caused by overfeeding — especially among new growers who assume more nutrients means more growth. Leaves turn an unnaturally dark green and curl downward at the tips in a distinctive 'claw' shape that's hard to miss. The key diagnostic differentiator: N-tox causes tips to curl DOWN with dark green leaves, heat stress curls leaves UP, and overwatering makes the whole plant droop uniformly. Excess nitrogen also blocks uptake of potassium, calcium, and magnesium — so you'll often see secondary deficiency symptoms stacking on top. N-toxic plants become more susceptible to pests and fungal disease because the lush, soft tissue is easier to penetrate. During flowering, it's especially damaging — the plant keeps pushing foliage instead of buds, delaying maturation, reducing potency, and producing harsh smoke.

Nutrient burn is one of the most common problems in cannabis growing — it's general salt toxicity from a nutrient solution that's too concentrated or from salts accumulating in the medium over time. The very tips of leaves yellow, then brown and crisp up, and unlike light burn (which hits the canopy tops) or single-element deficiencies (which target specific leaf zones), nute burn affects leaves throughout the entire plant simultaneously. It's especially common with synthetic fertilizers and in coco or hydro setups where salts build up fast. It often co-occurs with nitrogen toxicity — if you're seeing dark green clawing leaves AND burnt tips, you're likely overfeeding across the board. Seedlings in "hot" soil (fresh compost or amended super-soil) can show burn within days. A slight tip burn is actually considered acceptable by many experienced growers as a sign you're feeding near max, but any progression beyond the very tips means you need to back off. Damaged tissue won't recover — you're watching for healthy new growth as the sign things are improving.