Iron is an essential nutrient required for production of chlorophyll in leaves. When iron is lacking in the soil, chlorophyll is not produced, leading to reduced health, increase in disease, and a shorter lifespan for affected plants. A common symptom of iron deficiency in landscape trees and shrubs is yellowing between the veins of the leaves (interveinal chlorosis). Iron deficiency is common in areas where alkaline soil restricts the uptake of iron from the soil and in sandy soils where there is low nutrient-holding capacity. Iron deficiency in small trees and shrubs is treated with multiple soil applications of sulfur and iron chelate fertilizers. This reduces pH and makes iron more readily available: the iron chelate fertilizer allows better uptake of the iron in alkaline soil. For larger trees, it is not practical to treat all the soil where their roots develop; trunk injection of an iron compound is the best solution. Trunk injections are done in autumn and their benefit can last several years in deciduous trees.
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