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Iron Chlorosis

Plant disorder

Description​

Iron chlorosis is a nutrient disorder in which a plant cannot obtain enough usable iron to make chlorophyll. It is not an infectious disease, and the soil may contain plenty of iron. The problem often arises when alkaline soil or bicarbonate-rich irrigation water makes iron unavailable to roots. Poor drainage, compacted soil, damaged roots, and excessive phosphorus can also interfere with uptake. Acid-loving plants, including azaleas, rhododendrons, and blueberries, are particularly susceptible when grown in soil that is too alkaline for them. The most characteristic sign is yellowing between the veins of young leaves while the veins remain green. As the disorder worsens, new leaves may become almost white, develop brown dead areas, or remain small; growth may slow. Severe cases can weaken a plant over time. Correcting the conditions that limit iron uptake is more durable than simply adding iron to leaves.

Symptoms​

  • Yellowing leaves
  • Brown or crispy leaf edges
  • Stunted growth

How to Identify​

Look first at the youngest leaves: iron chlorosis usually starts as yellow tissue between distinctly green veins. Older leaves may initially look normal. Nitrogen deficiency generally yellows older leaves more uniformly, while magnesium deficiency usually begins between the veins of older leaves. Manganese deficiency can resemble iron chlorosis on young leaves and may cause small dead specks. Check whether the plant is suited to the soil pH, and test the soil rather than assuming it lacks iron. Inspect drainage and roots, too: waterlogging or root damage can cause similar yellowing by preventing nutrient uptake. A soil test and, when needed, a laboratory leaf-tissue test can help resolve uncertain cases.

Prevention​

Choose plants suited to your soil, or test its pH before planting species that need acidic conditions. Follow soil-test recommendations when adjusting pH; changing it is gradual, and adding too much acidifier can harm plants. Maintain good drainage and avoid compacting soil around roots. Water deeply as needed without keeping the soil continuously saturated. If irrigation water is highly alkaline, seek local advice on managing its effect on soil pH. Use fertilizer at recommended rates, particularly phosphorus, rather than applying extra nutrients in hopes of preventing yellowing. Protect roots during digging and cultivation, and maintain an appropriate layer of organic mulch without piling it against stems. Periodic soil tests are useful where iron chlorosis has recurred.

Treatment​

Start by checking soil moisture and drainage. Correct overwatering, relieve compaction where possible without damaging roots, and pause unnecessary fertilizer applications. Test soil pH before adding amendments. If pH is too high for the plant, elemental sulfur may lower it gradually when applied at a soil-test-recommended rate; it is not an immediate fix. Where soil pH cannot readily be changed, a labeled iron chelate applied to the soil can provide iron. Fe-EDDHA generally remains effective in alkaline soil; other chelates may be less effective there. Follow the product label for rates and placement. A labeled foliar iron spray can green treated leaves more quickly, but its effect is temporary and new growth may still be yellow. Test a small area first, spray as directed, and avoid hot conditions that increase leaf-burn risk. Do not rely on rusty nails or excessive iron sulfate as substitutes for correcting the underlying problem.

Plants Affected​

Azalea, Bald Cypress, Blueberry, Camellia, Cleyera, Enkianthus, Fothergilla, Gardenia, Gaultheria, Halesia, Heath, Heather, Hydrangea, Ilex, Kalmia, Leucothoe, Middlemist Red, Mountain Laurel, Pieris, Pin Oak, Poncirus, Red Maple, Rhododendron, River Birch, Saucer Magnolia, Scarlet Oak, Skimmia, Southern Magnolia, Sugar Maple, Vaccinium, Willow Oak, Winterberry, Zenobia

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