Pin Oak in Limestone Soil: Iron Chlorosis, Not Mulch

Pin Oak Upper Limbs Dead in High-Lime Soil: Iron Deficiency

Pin oaks hate limestone (pH >7.5). Causes iron chlorosis—yellow/green leaves, dieback. Mulch is not the problem; pine straw mulch actually helps acidify.

Treatment Options

• Iron chelates in soil holes (6" deep, 1.5" wide, 1 ft apart, concentric rings).
• Foliar chelate spray (temporary, hard on large trees).
• Sulfur + iron products to lower pH (impractical if soil has free lime).

Long-Term

Pin oak is poorly suited to calcareous soils. Consider replacement with tolerant species (bur oak, chinkapin oak, hackberry).