Iron Chlorosis in Pin Oaks: Diagnosis and Soil Treatment

Pale yellow leaves with green veins on pin oaks indicate iron chlorosis—iron unavailable due to high soil pH (>7), clay, or root damage from construction. Red maples nearby thrive because they tolerate those conditions better.

Treat by auguring 12–18 inch holes 18–24 inches apart under the drip line, filling with equal parts ferrous sulfate and elemental sulfur (2 lb total for small trees). Use inorganic iron sources (ferrous sulfate 20% Fe). Avoid chelates for soil application. Retest pH long-term.