How to Spot Nutrient Deficiencies in Plants

By nutrient

• Nitrogen (N): uniform yellowing of older/lower leaves first; overall pale, slow growth.
• Phosphorus (P): purplish/reddish or bronze tint on older leaves; stunted.
• Potassium (K): yellowing with brown, dead, scorched leaf margins on older leaves; newer leaves stay green.
• Iron (common in high-pH soil and blueberries): yellowing between the veins of NEW leaves, veins staying green.

Before you feed

Deficiency-like symptoms are often not a true shortage — overwatering, root damage, cold soil, or a pH that locks nutrients up can all mimic them. A soil test is the reliable way to know what (if anything) to add, and how much. Adjusting pH is frequently more effective than adding more fertilizer.

⚠ Don't guess-and-dump fertilizer. Confirm with a soil test, and check pH first — nutrients present in the soil can be unavailable if the pH is wrong.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• West Virginia University Extension — Nutrient Deficiencies in Plants — Nitrogen deficiency causes uniform yellowing of older leaves; phosphorus causes purpling of older leaves; potassium causes marginal yellowing/scorch of older leaves.
• University of Georgia Extension — Nutritional Deficiencies in Vegetables — Deficiency symptoms differ by nutrient and leaf age; a soil test is recommended to confirm before correcting.

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