Dear Reader,
Nutrient deficiency such as with iron or manganese, is no joke for trees. It can lead to reduced growth, wilted leaves, and with enough time, death of the tree. One common symptom of iron or manganese deficiency is chlorotic leaves: the pale yellowish green discoloration of leaves. Today, I would like to talk about the who, what, when, where, and whys of nutrient deficiencies along with how to resolve this issue.
Iron or manganese deficiency in trees occurs when a tree’s roots are unable to take up these minerals from the soil. Some may believe that this is due to a lack of said nutrients in the soil, but in most cases, it is due to the high pH of the soil. pH is used to measure how basic or acidic a solution is. 0 is highly acidic, 14 is highly basic, and 7 is considered neutral. When the soil is too alkaline (basic) for the plant, the mineral nutrients are in a difficult form for roots to take up.
Many parts of Ohio contain highly alkaline pH soil. This is due to the parent material deep below the surface. Starting from the surface of the ground to the bottom, there are four horizon layers: O, A, B, and C. Each horizon is deeper than the next and there are less and less organic materials and clay. Below horizon C is the parent material that makes up the content of the soil above it. The parent material around much of Ohio, mostly in northwestern Ohio, contains limestone, which has a high pH. Marble, a high pH metamorphic rock, along with limestone, is heavily present in the parent material around Columbus and central Ohio. Would it come as a surprise that Marble Cliffs, Ohio has a lot of marble (and limestone) or that the soil in central Ohio has a high pH? Some studies have also shown that soils near freshly poured concrete have a high pH due to leaching of limestone from the concrete to the soil.
Trees with iron or manganese deficiency may have chlorotic leaves due to chlorosis. Chlorosis is a condition where leaves produce insufficient chlorophyll which leads to a yellow, white, or pale discoloration. If you look at the images below, one may argue that chlorotic leaves look visually appealing, but what cannot be argued is that it is a sign of poor tree health. Without treatment, a tree’s growth will be stunted and its leaves will begin to wilt or develop spots. With enough time, the tree will eventually die. Although chlorosis is a result of iron or manganese deficiency, it may also be a result of insect problems, disease, drought, soil compaction, or poor drainage. Before treating your tree for nutrient deficiency, it is important to identify that it is indeed your tree’s issue. If unclear, the best solution would be to send a soil sample to a lab to determine the issue. In central Ohio, trees to watch out for include pin oak, red oak, shingle oak, sawtooth oak, maple, sweetgum, river birch, holly, and sweetbay magnolia. I have also been told in my World of Plants class at The Ohio State University that people in central Ohio should avoid planting rhododendrons because they too do not survive well in highly alkaline soils.
Chlorosis in a pin oak tree
Chlorosis in a river birch tree
So let’s talk about how to resolve iron or manganese deficiency. The best solution is to avoid plants that favor acidic soils, such as the trees mentioned earlier. When selecting trees and plants, favor locally sourced when possible since they will be adapted to local soils. If a tree is chlorotic due to high soil pH, seasonal fertilization with iron and/or manganese supplements will be necessary. There are various ways that this can be done. Remember that the parent soil will continue to raise pH over time, so treating the soil with aluminum sulfate or elemental sulfur seasonally will help lower soil pH, making existing iron and manganese more available to plants.
Hopefully you enjoyed reading this article and learned a fact or two as I did in my World of Plants class at The Ohio State University and while researching more on this topic. Thank you for reading! For more information about soil, leaves, and fertilization, I will share two links to similar articles written by TJ Nagel and José Fernández.
The Importance of Green Leaves by TJ Nagel: https://www.russelltreeexperts.com/arbor-ed/2018/7/17/d686ziqwja9frp132ba4btg8owmtsk?rq=Chlorosis
Test Before Treatment: Soil & Tissue Testing by José Fernández: https://www.russelltreeexperts.com/arbor-ed/2018/11/5/tree-science-soil-amp-tissue-sampling?rq=Chlorosis
Sincerely,
Enrique Arayata I Video Production Assistant, Russell Tree Experts
Enrique is a second year student at The Ohio State University majoring in moving image production with a double minor in photography and film studies. In his free time, he enjoys running, spending time with his girlfriend and family, photography, and creating YouTube videos.