URBANA, Ill. — Do you have a tree that is displaying fall color early this year?
Although some early color may be beautiful, this may be a sign of health issues.
“A branch or two here and there, or some yellow leaves in the canopy are not always cause for alarm, but if the majority of your tree’s canopy is changing color early, it may be a cry for help,” said Ryan Pankau, a horticulture educator with University of Illinois Extension.
Trees that change color early are typically exhibiting a plant response to some kind of environmental stress. The first step to helping your tree is to identify the problem.
Begin by considering any recent changes to the tree’s growing space. Has there been any soil disturbance such as construction? Do you know of any other recent major disturbances?
Next, inspect the base of the tree. Do you see any visible damage from animals or machinery? Is there a “girdling root” encircling the trunk and strangling the root system?
“In some cases, the damage a tree has experienced may be irreversible,” Pankau said. “Unfortunately, extensive trunk damage cannot be repaired.”
Finally, inspect the canopy of the tree for any clues. Does the tree have unusually small or deformed leaves? Is the annual growth from last year — identifiable on twigs by locating the previous year’s terminal bud scale scar — significantly less than past years?
“I have most commonly observed this issue in newly planted trees, which are under transplant stress for several growing seasons,” Pankau said.
The first few years after being transplanted are tough times in a tree’s life and some added stress this time of year, in the form of hot, dry weather, can be the impetus for your tree’s call for help.
In many urban settings, soil compaction or poor drainage have a major impact on tree health and correcting soil issues can be quite difficult. Therefore, many times the only practical way to help your tree is to follow some general recommendations for boosting tree health. Any bit of help you can provide may be enough to get your tree through these stressful times.
Often, the best recommendation for a tree showing signs of stress this time of year is watering, and trees need more water than you might expect. Although 90% of tree roots are located in the top 12 to 15 inches of soil, turfgrass often steals the rainfall during smaller rain events.
Since turfgrass has a dense root system concentrated in the upper 2 to 6 inches of soil, it is able to outcompete trees when a rainstorm does not thoroughly saturate the soil profile.
“To effectively water a tree, the soil needs to be saturated beyond the area beneath the tree’s canopy,” Pankau said. “By extending watering beyond the spread of the branch tips, new root development is promoted in that area, which helps build a robust root system.”
In order to achieve soil saturation and avoid runoff, water slowly over a long period of time.
“If you are using a typical garden sprinkler, I recommend allowing it to water for at least two hours in order to saturate the soil enough to reach roots of a large mature tree,” Pankau said.
Smaller, younger trees may take less time. In general, you should plan to provide the equivalent of a 1- to 2-inch rainstorm every two weeks during the hot, dry part of late summer and early fall. To conserve water, consider using a soaker hose or drip tape for more efficient watering.
Another factor that can vastly improve the water holding capacity of the soil, and eliminate competition from turfgrass, is mulch. If possible, mulch your tree out to the dripline of the canopy.
Apply mulch 4 to 6 inches deep as it will settle dramatically over the next several months. This protective layer will help retain soil moisture, reduce or eliminate weed and grass competition and, over time, will add organic matter to the soil.
“In addition, adding mulch may help protect your tree from future mower damage by leaving a buffer between it and the mower deck,” Pankau said.