CANNABIS EXPLAINER
Cannabis Leaf Symptoms Guide
Leaf color and texture tell you what your cannabis plant needs.
CANNABIS EXPLAINER
Leaf color and texture tell you what your cannabis plant needs.
| Symptom | Likely Cause | Fix |
|---|---|---|
| Yellow lower leaves | Nitrogen deficiency | Add nitrogen-rich fertilizer |
| Brown leaf tips | Nutrient burn / overfeeding | Flush and reduce feeding |
| Curling up leaves | Heat stress or overwatering | Lower temps or reduce water |
| Purple stems | Phosphorus deficiency or genetics | Check pH, add phosphorus |
| Spots with yellow halos | Calcium deficiency | Add cal-mag supplement |
| Mottled yellow pattern | Magnesium deficiency | Foliar magnesium spray |
Yellow leaves are the most common cannabis plant symptom and can indicate several different problems. Yellow starting from the bottom: classic nitrogen deficiency — the plant is moving nitrogen from lower leaves to upper growth. Yellow spreading from between leaf veins while veins stay green: magnesium or iron deficiency. All-over yellowing in seedlings: overwatering or root rot. Always check pH first — nutrient lockout due to wrong pH is the cause of most "deficiency" symptoms.
Browning leaf tips that curl downward usually indicate nutrient burn from overfeeding. Reduce your nutrient concentration and flush with plain pH-adjusted water. Brown spots in the middle of leaves often indicate calcium deficiency or fungal infection. Rust-colored spots with yellow halos may be caused by calcium or magnesium issues, especially in coco or hydro grows. Check your cal-mag levels.
Leaves curling upward (taco-ing) indicate heat stress or overfeeding. Lower your grow room temperature to 72-82°F and check that air circulation is adequate. Leaves curling downward (clawing) in nitrogen-dark green leaves indicate nitrogen toxicity from overfeeding. Leaves drooping with wet soil indicate overwatering — let the medium dry out between waterings. Twisted or wavy new growth may indicate pH instability or broad mite infestation.
Most cannabis nutrient deficiency symptoms are actually pH-related lockouts — the nutrients are present but unavailable at the wrong pH. Optimal pH: soil 6.0-7.0, hydro/coco 5.5-6.5. Check and adjust your water and runoff pH before adding more nutrients. A $20 pH meter is one of the most valuable tools for any cannabis grower.