Fixing Iron Chlorosis in Aspen Trees: Soil pH and Iron Treatments

Aspens in Albuquerque, NM (6,200 ft elevation) show yellow leaves with green veins — classic iron chlorosis from alkaline soil. Owner asks if vinegar can lower pH.

Why Iron Becomes Unavailable

Soil pH above 7.0 converts iron to insoluble forms. Alkaline soils (common in Southwest) prevent uptake even when iron is present.

Effective Treatments (Vinegar Won't Work)

You cannot add enough vinegar to significantly lower soil pH at root depth (18-24 inches). Instead:

1. Iron Sulfate Soil Application

• Bare soil: 1 lb per ½ inch trunk diameter (measured at 4 ft) under canopy.
• Turf: Deep-feed via liquid injection or holes drilled 15-18" deep, 2 ft apart, in concentric circles from 2-3 ft from trunk to 3 ft beyond dripline.
• Lasts 2-3 years. Best applied early spring at bud swell.

2. Chelated Iron (for pH >7.2)

Use EDDHA chelates only: Sequestar 6%, Sprint 138, Millers FerriPlus. Follow label rates.

3. Sulfur + Iron Sulfate Mix (1:1 ratio)

• Trees ≤4": 1 lb each per inch trunk diameter.
• Trees >4": 2 lbs each per inch trunk diameter.
• Sulfur locally lowers pH, making iron available.

Foliar sprays give quick but temporary relief. Soil treatments address the root cause.