Diagnosing Nutrient Deficiencies
Leaf symptoms are your plant's way of communicating problems. This guide teaches you to read the signs and respond correctly.
The Golden Rule: Check pH First
Before assuming any deficiency, check your pH. Most so-called deficiencies are actually pH lockout — nutrients are present but unavailable at the wrong pH. Soil: 6.0–7.0. Hydro/coco: 5.5–6.5. Fix pH first, wait 3–5 days, then reassess. This single step solves the majority of "deficiency" cases.
Mobile vs Immobile Nutrients
Mobile nutrients (N, P, K, Mg) can move within the plant from old growth to new growth. Deficiency symptoms appear on OLDER, LOWER leaves first. Immobile nutrients (Ca, Fe, Mn, B) cannot move once deposited. Deficiency symptoms appear on NEW, UPPER growth first. This distinction tells you which nutrient to investigate.
Common Deficiency Symptoms
Nitrogen: uniform yellowing of old leaves moving up the plant. Calcium: brown spots with yellow halo on new growth, distorted tips. Magnesium: yellowing between veins on older leaves (interveinal chlorosis). Iron: yellowing between veins on new growth. Phosphorus: purple/dark red stems and leaf undersides. Potassium: brown, necrotic leaf edges.
Diagnosing Overfeeding
Nutrient burn shows as brown, crispy tips on otherwise healthy leaves. It progresses inward if uncorrected. Caused by too-high EC or too much of a specific nutrient. Solution: flush with plain pH-adjusted water until EC drops, then resume feeding at lower strength.
Quick Tips
- Take photos of symptoms with a ruler or leaf for scale — helps track progression over days.
- Do not chase every yellow leaf — some lower leaf yellowing in late flower is completely normal.
- One problem at a time — make one change and wait 5–7 days before making another adjustment.