Field Identification
Iron deficiency shows as interveinal chlorosis on newest leaves while veins stay greener and older foliage looks relatively normal. It is common in high-pH soils where iron is insoluble, in waterlogged roots, and in containers with alkaline irrigation water. The plant is not always short of iron in the site -- uptake can be blocked by cold soil, root damage, or competing ions. Fixing the underlying cause beats endless foliar greening sprays.
Compare with magnesium deficiency, which shows on older leaves as interveinal yellowing with a different pattern. Test irrigation water alkalinity if pots on concrete patios show chronic chlorosis. Root inspection for rot, girdling, or nematode lesions explains many cases where soil tests say iron is present. Tissue analysis of new leaves confirms low iron when lab methods match your crop.
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How to Deal With It
Organic Control Methods
Healthy mycorrhizae and humic acids from compost improve iron chelation in acidic organic soils. Siderophore-producing bacteria make iron more available in the rhizosphere under some conditions. These effects are gradual and work best when pH and drainage are already reasonable. They do not override pH 8 water on acid-loving plants in pots.
Acidify root zones only when soil tests and crop requirements justify it -- sulfur or suitable amendments per extension tables. For chlorotic blueberries on alkaline native soil, grow in raised beds of peat-leaning mixes or choose tolerant cultivars. Chelated iron drenches help containers when label matches your pH range. Fix drainage before chasing micronutrients on yellow wet roots.
Avoid excessive phosphate fertilization that can tie up micronutrients on sensitive species in some soils. Mulch to moderate soil temperature so spring roots access iron sooner. For trees with stem girdling roots, air spade remediation restores uptake more than foliar iron ever will.
Aerate compacted lawns with interveinal chlorosis on high-pH soils after addressing drainage. Remove plastic burlap and wire from root balls at planting so roots can explore amended backfill. Rinse salt spray from coastal hedge leaves with plain water when permitted.
Chelated iron foliar sprays (Fe-EDDHA where needed for high pH) green up new growth within days but do not fix pH. Ferrous sulfate sprays stain concrete and clothing -- mask nearby surfaces. Compost tea is inconsistent as an iron source -- prefer known chelates when deficiency is confirmed. Repeat applications are needed until underlying cause is corrected.
Let Nature Handle It
Natural Enemies
- Beneficial Fungi
- Competitive Microbes
- Antagonistic Bacteria