By: Ron Gumz Certified Arborist MN-0324A
As you gaze around the landscape, you may notice many colors of various trees and shrubs, especially of the foliage. You can appreciate the color of a blue spruce, the maroon in a Crimson King Maple, spring's golden color of a Sunburst Honeylocust, or the white tones of a dappled Willow. These special colors are more of an exception than the rule. Most trees are designed to have green foliage. When trees (that are supposed to be green) start looking a pale yellow color, it can be a sign that the tree is suffering from a condition called chlorosis.
Chlorosis is a yellowing of the foliage due to the loss or breakdown of chlorophyll. Chlorophyll is responsible for the green color in leaves. As chlorosis worsens, leaves lose their ability to use light energy to create food from photosynthesis. This can reduce the growth in the tree, use up the energy reserves and subject the tree to secondary issues. A weakened tree may begin to lose branches throughout the crown and this eventually leads to death.
Chlorosis is usually a gradual process; it may take several years to become noticeable. This condition can be difficult to control. If it has taken some time for the tree to become chlorotic, it may take some time for the tree to recover from the chlorosis.
Certain trees tend to show symptoms more frequently than others do. Oaks, birches, silver maples and red (rubrum) maples tend to be especially susceptible to chlorosis in this area. Some causes for chlorosis are mineral deficiencies, high soil pH, damaged or compacted roots, and construction activities. These conditions limit the tree's ability to absorb the nutrients and micronutrients it needs to maintain its color.
Maintaining a healthy tree is a good way to avoid problems with chlorosis. There is hope for trees that do become chlorotic. Improving the root system of the tree is important in combating chlorosis. This may be done with root biostimulants, mycorrhizae inoculation, mulching and proper watering. Sometimes supplementing the tree with nutrients can also help combat chlorosis. Fertilization, micronutrient fertilization with iron and/or manganese, compost teas, and macro-infusion of nutrients into the trunk are all methods to help a tree combat the issue of chlorosis.
Recommendations will vary depending on the type of tree, the time of the year as well as other issues. Homeowners are often the first to notice that a tree may not be looking as green as it may once have been. Mid to late summer is a good time to evaluate a tree for chlorosis. Contact your Wachtel Tree Science Certified Arborist now if you would like to see your tree be healthy and green again.