Nutrient deficiencies: visual ID by leaf symptom

Visual diagnosis of nutrient deficiencies is one of the more practical skills in horticulture -- if you understand two biological principles, you can narrow most deficiency diagnoses rapidly without laboratory.

Visual diagnosis of nutrient deficiencies is one of the more practical skills in horticulture — if you understand two biological principles, you can narrow most deficiency diagnoses rapidly without laboratory testing.

The two principles: (1) Mobility — some nutrients move within the plant from old to new growth; others don't. (2) Pattern — each nutrient causes a characteristic distribution of symptoms on the leaf (whole leaf yellowing vs. interveinal chlorosis vs. marginal burn).

The mobility framework

Per Penn State Extension, nutrients are classified as mobile or immobile within the plant:

Mobile nutrients (move from old to new growth when deficient): N, P, K, Mg, Mo. When these are deficient, the plant relocates them from older, lower leaves to new growth at the shoot tips. Symptoms appear first on older (lower) leaves.

Immobile nutrients (cannot be relocated once deposited): Ca, Fe, Mn, Cu, Zn, B. When deficient, the plant cannot supply enough to new growth from old tissue. Symptoms appear first on new (upper) leaves and young tissue.

This mobility rule is the fastest diagnostic filter.