Iron deficiency in trees and shrubs is a common problem that can have a serious impact on plant health. All trees and shrubs need nutrients to grow and develop. Iron is one such essential nutrient that trees need.
Why is Iron Important for Trees
Trees need iron for the production of chlorophyll in leaves. When iron is lacking, plants cannot produce the necessary chlorophyll. As a result, that tree or shrub cannot make enough food. Ultimately, the affected tree or shrub will suffer from reduced health, an increase in disease, and a shorter lifespan.
Iron deficiency is common in areas where alkaline soil restricts the uptake of iron from the soil. Additionally, trees and shrubs growing in sandy soils where there is low nutrient-holding capacity are at risk. In the latter, the soil is unable to effectively hold on to nutrients.
Signs of Iron Deficiency
A common symptom of iron deficiency is interveinal chlorosis. This is when there is a yellowing of leaves between the veins. To clarify, the leaves will turn yellow and the veins will remain green. The discoloration is a clear indication of the lack of chlorophyll, which is the green pigment responsible for photosynthesis. In severe cases, leaves will begin to brown around the edges. Eventually, the leaves will fall off and the twigs will start to dieback.
If you notice yellow leaves on your trees and shrubs, you want to act quickly to identify the underlying issue. Some other nutrient deficiencies may display similar symptoms to iron chlorosis. The best course of action is foliar and soil nutrient analysis, including a pH measurement. Importantly, if the plant is treated with the wrong nutrient, the problem can be made worse. Therefore, soil analysis is critical to identify if iron is lacking or there are other concerns.
While iron deficiency can affect nearly any tree or shrub species, there are some that are more susceptible. Examples include pin oak, white oak, red oak, azalea, rhododendron, magnolia, birch and photinia.
Treatment Options
After soil analysis identifies iron deficiency, treatment will depend on various factors including the size of the impacted plant. Small trees and shrubs will require 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 generally not practical to treat all the soil where their roots develop. Here, the best solution is trunk injection of an iron compound. Schedule trunk injections in the fall or winter so that their benefit can last several years in deciduous trees. Conversely, treatments in spring or summer are applied at a lower concentration so as not to damage the leaves. As such, these treatments tend to be effective for only one growing season.
