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This month’s Tree Tip was written and researched by Britt Hubbard ISA Certified Arborist #SO-5792A and Forester. He may be contacted directly via email with any questions concerning this article or any tree related issues.
Do your plants have yellowing leaves, dead leaf margins, misshapen leaves, or dieback in the tips of stems? While these issues can be the result of several causes, one possibility is nutrient deficiencies. There are 16 elements essential to the life process of trees. Without these elements, trees and shrubs will not survive. Three of the elements (Carbon, Oxygen, and Hydrogen) are available in the air. The remaining thirteen (Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulfur, Iron, Manganese, Boron, Zinc, Copper, Molybdenum, and Chlorine) are absorbed from the soil.
Most of the native soils in Tennessee and Mississippi do not have nutrient deficiencies. However, deficiencies do occur in landscapes where the soil has been altered through the removal of topsoil/organic matter, compaction, grade changes, or through irrigation with water that is high or low in certain elements. The previous sentence describes most neighborhoods and urban developments where we work and live.
Three of the most commonly deficient nutrients are Nitrogen, Iron, and Manganese. When deficiencies of these nutrients become extreme, symptoms are visible. The symptoms are an excellent warning that the tree is having problems.
Nitrogen deficient trees and shrubs exhibit a uniform yellowing of leaves (chlorosis). Leaves may also have more pronounced fall color, premature leaf drop, and the tree may develop small premature fruit. Treating nitrogen deficiencies is usually performed through fertilizing by broadcasting over the surface or preferably through deep root fertilization (see April’s Tree Tip for deep root fertilization information). The treatment will get Nitrogen to the tree’s roots which will then be taken up by the tree. It is best to periodically treat for nitrogen deficient soils.
Iron deficient trees and shrubs also exhibit a yellowing of leaves, however it is not uniform on the leaf or throughout the tree. In iron deficient leaves, the veins remain dark while the surrounding tissue turns light green to yellow. Some trees may only have a single branch showing symptoms while rest of the tree appears normal. Treatments include soil surface applications, deep root injection (preferred), and foliar sprays. Iron deficiency can also be an issue when soil pH is high. High soil pH ties up iron in the soil making it unavailable for the plants. This is very common in soil around new buildings that has been contaminated by lime in mortar from block, brick, or stucco. Lime raises the pH limiting iron availability. In this case, soil pH should be addressed to make the nutrient available.
Manganese deficient trees have symptoms similar to iron deficiency. Leaves in trees appear yellow with green veins. Leaves may also appear limp and fruit may be smaller than normal. Treatments include foliar sprays and soil applications. Like iron, Manganese is not available in soils with high pH and should be addressed when it is factor limiting Manganese availability.
The remaining ten nutrients, although less commonly a problem, can cause serious problems for trees and shrubs when deficient. Any time a nutrient deficiency is suspected, the first step toward correcting the issue is to get the soil tested. A soil test will show what nutrient is deficient, whether or not pH is a factor, and the quantity of nutrient needed to correct the problem.
Soil test results should be interpreted by an arborist or other knowledgeable professional. The arborists at Woodland Tree Service are more than happy to evaluate your tree, take a soil sample, analyze the soil test results, and implement a plant health care program, tailored to your tree, to correct nutrient deficiencies and any other tree issues you may have.
If you need any assistance with your trees, please contact the experts at Woodland Tree Service. Email firstname.lastname@example.org or call us at (901) 309-6779.