Why Do Perennials Turn White?

Function of Iron

• The deficiency of iron occurs in perennials either because the soil is deficient in the nutrient or because an excessive amount of some other nutrient like phosphate or bicarbonate reduces the plant's ability to absorb iron. The discoloration occurs when the green chlorophyll in leaves stops developing. Even though iron is not a component of the chlorophyll molecule, it is required for the synthesis of chlorophyll in all plants, including perennials.

Symptoms

• Iron chlorosis starts with an interveinal chlorosis, or the yellowing of leaves with only the dark green veins retaining their color. If the deficiency is not fixed, the discoloration continues to increase to an extent where the entire leaves become yellow or white. The next stage is the death of the leaves, starting from the outer edges that scorch and turn brown with cell death. Often only certain areas of the perennial plant display symptoms of chlorosis while the rest of the plant remain healthy.

Cause

• Iron deficiency is most common in perennials that are growing in excessively alkaline soils where a pH of 6.5 of more binds the iron and prevents roots from accessing it. Excessive levels of manganese, zinc, copper or phosphorus in soil are also common causes of iron chlorosis. Plants that are growing in poorly drained, compacted soils are prone to suffer from the deficiency.

Solution

• Apply chelated iron fertilizers like Fe-EDTA, Fe-EDDHA or Fe-DTPA to the soil. In chelated fertilizers, iron is mixed with the chemical called chelate that keeps the iron in plant-accessible forms as opposed to the non-chelated fertilizers. Recommended rates of application are 2 to 3 lbs. of fertilizer for 1,000 square feet of soil. Apply sulfur to the soil to reduce soil pH as a long-term solution. Reduce compaction in soil by aeration, improve drainage and avoid overwatering the perennials.