"Why is my tree losing leaves and turning brown?" This summer I’ve been getting this question (or others like it) more than usual. I have worked with the Extension Service for a few years now and, though I have seen many tree problems, I haven’t seen as many dying trees as I have this year. Why are we having this problem and what can we do?
Oak, hickory, dogwood and other trees have been losing leaves, browning at the edges of their leaves or dying suddenly without any apparent reason. If we could look at the roots though, the reason would probably become apparent.
Often when leaves suddenly dry up and die on a plant it is due to a stem or root problem. Stem damage, especially by string trimmers and lawn mowers can open the tree up to rots which weaken the tree. Check your tree for damage. Once damage occurs, it is too late to do much. We do not recommend putting anything on the wound, just prevent further damage. Kill the grass around the base of the tree and replace with mulch so mowers and string trimmers will not be used close to the tree. I can’t stress enough that its important in some situations to choose a tree or grass, sometimes you can’t have both.
Most shade tree decline is probably due to drought and flooding. The roots of a tree are in the top 8 to 12 inches of soil. When this soil is very dry or saturated with water for a long time, the tree's feeder roots begin to die. The feeder roots are the small, fine white roots. They take up most of the water and nutrients for the tree. The tree must replace these roots to survive. The continued bad weather we have had over the past few years has damaged trees and made it impossible for many to recover. The result is trees that die suddenly without apparent reason. We call this condition shade tree decline.
What can you do? By the time the tree shows symptoms it is often too late. Trees have large reserves of food and water stored up. When they suffer enough damage to kill them, it may be a year or more before they actually dry up and die. This is why a tree may die due to drought or flooding that happened long ago. In the case of this year we had long prolonged droughts last year and lots of rain this year. This can lead to trees being weaker than usual to environmental stresses from this year and from previous years.
Shade tree decline weakens trees making them more susceptible to pests. I have noticed dying trees with beetles in them. Weak trees can also have problems like slime flux (an oozing liquid from the stem), cankers or leaf spots. However, the main problem is tree decline. This must be addressed to solve the problem.
The key is preventing shade tree decline. Keep the tree vigorous throughout its life. When planting, pick a site that is suitable to the tree you are planting. For instance, do not plant dogwoods in full sun, they like partial shade. Prepare the site well before planting - digging a planting hole at least 2 to 3 times wider than the root-ball. It is best to till up a large area to plant the tree in. Till the area 8 to 12 inches deep. If plants are grown in a container, loosen roots in the root-ball before planting. For balled and burlapped trees, remove the burlap from the top of the ball being careful not to damage the ball. Plant the tree at the same level it was originally growing. Never plant trees deeper that they were growing before transplanting.
For established trees, stay away from trees with mowers, trimmers and heavy equipment. Even if equipment has not hit the tree, driving over the roots compacts the soil and can kill roots. Digging deeply around trees or filling around trees also kills roots and weakens trees. When filling around trees, remember the general rule that states that placing six inches of soil over the roots of a tree has a 50% chance of killing the tree.
One the most important things you can do for your tree is water it. During dry times, water the soil to a depth of 7 inches every 4 days. To do this will require 3/4 to 1 inch of water each time. If using a sprinkler, place a pan under it when watering and time how long it takes to put out enough water. Then you can water this long each time. Do not water lightly each day. This causes problems by encouraging a shallow root system making the tree susceptible to drought and cold weather.
Proper watering is extremely important and may have saved many trees if done during the drought. Once trees show signs of stress, it may be too late to help them. However, if the tree has green leaves on it, continue to care for it. It may recover.
For further information on shade tree care, contact me at the county Extension office. We have brochures on shade tree decline, selecting trees, tree planting and care of storm damaged trees. Come by our office or call 912-653-2231 in Pembroke or in Liberty county at the office in Hinesville at 912- 876-2133 for more information. You can also contact me by email at uge3029@uga.edu or at uge3179@uga.edu in Liberty County.