Plant Problem Diagnosis Key / Nutrient problems
Nutrient
Iron deficiency
Fe
Iron does not move out of old leaves, so new growth yellows first. It is rarely missing from the soil; it becomes unavailable at high pH, with high-bicarbonate water, or with excess phosphorus.
Signs
- New leaves pale yellow between a fine, sharp net of green veins.
- Older leaves stay green.
- Common in alkaline soil and in hydroponics with pH above about 6.5.
What favors it
High pH (above about 7 in soil, 6.5 in hydroponics), excess phosphorus, manganese, zinc or copper, and high bicarbonate water.
Prevention
- Keep root-zone pH in the crop's range.
- Use chelated iron suited to the pH: EDTA below about 6.5, DTPA to about 7.5, EDDHA above that.
- Acidify high-bicarbonate irrigation water.
Often confused with
Sources
- Nutrient Deficiency of Trees and ShrubsUniversity of Maryland Extension
- The Importance of Iron in Vegetable Crop Nutrition in North CarolinaNC State Extension
- How to Prevent Iron Deficiency in Iron-Inefficient Greenhouse CropsUMass Extension
- Iron fertigation strategies for iron chlorosis in high-pH soilless media (HortScience 60:3, 2025)HortScience
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
No, only damage or discoloration - Where is the problem?
A tree or shrub - Which part of the tree or shrub shows the problem?
Leaves of a broadleaf tree or shrub - What do the leaves show?
Pale, yellow, speckled or bleached - What do the leaves look like up close?
Pale yellow with green veins
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on iron deficiency, or find a plant diagnostic lab through your state's Extension.