Diagnosing Marginal Chlorosis on Sago Palms (Cycas revoluta)

Symptom Analysis

One of two adjacent sagos shows new fronds yellowing from the edges inward, while the other remains healthy. Roof runoff was suspected, but physical damage from water would cause different symptoms. The pattern suggests nutrient deficiency—magnesium, potassium, or iron—exacerbated by high soil pH or leaching in sandy soil.

Nutrient Deficiency Signatures

Magnesium: Uniform yellow/orange margins with green centers, no necrosis.
Potassium: Gradual orange-bronze discoloration from tip to base, often with leaflet necrosis.
Iron: Interveinal chlorosis on newest growth, worse at high pH.

Action Plan

Apply a slow-release palm fertilizer with micronutrients (Mg, Mn, Fe, Cu). Test soil pH; if above 7.5, acidify with sulfur. Avoid random chemical sprays. Monitor new flush for improvement.