October 2005
Autumn Arbor
Drought leads to trickier
tree care this fall
by Susan DeGrane
Many people think the only time to plant trees is in the spring. But autumn is also a good option, as long as you get the trees into the ground so their roots have time to take hold before the bitter cold.
And just because the temperature and leaves are falling doesn’t mean you should stop watering or caring for your trees. But this year, tree care can be trickier due to the summer drought. For instance, arborists caution that before you grab those pruning shears consider that some of the branches may have just gone dormant from the drought. In fact, it may take a while to gauge the tree damage caused by this year’s dry conditions.
Newly transplanted trees with pared-back root systems are the most vulnerable to water deprivation, said Jim DeHorn, overseer of TreeKeepers, a group of 700 volunteer arborists certified by the Openlands Project to help maintain trees in public areas throughout northeastern Illinois.
“If the ground is not saturated with heavy fall rains by Thanksgiving, the trees will suffer,” said DeHorn. “Most of us won’t really know which trees have died until they fail to leaf out in spring.”
The timeline for tree damage may extend even further, according to Rex Bastian, of The Care of Trees, a private company. “We’re going to be seeing tree problems next year and for probably the next two to three years,” he said.
Since rainfall for northern Illinois remains below normal, and given the deep-down dryness of the soil, it’s still important to continue to water trees this fall.
Even so, be careful not to over-water. “A lot depends on the location of the tree and the condition of its root system,” said Bastian. “A good way to be sure if the soil has enough moisture is to get down on your hands and knees and dig with a trowel.” Soil eight inches down — the depth of most tree roots — should be moist, not soggy.
Fall also is a great time to place mulch around trees. Mulching provides a myriad of benefits, from retaining soil moisture to encouraging forest-like soil conditions in which trees thrive.
“A lot of people don’t realize that grass is really bad for trees,” said Bastian. “You don’t find grass in the forest.” Also, lawnmowers are notorious for damaging tree roots — another reason to avoid allowing grass near trees.
Wood chips, piled four inches deep, can serve well as a buffer, but don’t put mulch directly on the tree base so you can avoid bark decay, disease and insect problems.
Perennial shade plants are better companions for trees than grass, Bastian said. Mulching in the fall prepares the soil for planting ground cover, hostas or flowers in the spring.
Exercise extra caution in pruning trees this fall. “Pruning causes stress, and the trees don’t need additional stress,” said DeHorn. You may want to consider postponing the process altogether until the spring.
And finally, if you plan to plant trees this fall, do so before mid-October, so the roots can take hold before the ground goes into a deep freeze.
Consider that native trees are more tolerant of weather extremes and, once established, require less watering.
The Morton Arboretum recommends the following native, drought-tolerant trees: Honey-Locust, Kentucky coffeetree, oaks, hickory and ash. Drought-tolerant traits include small, thick leaves with silvery — sometimes even hairy — reflective surfaces and the ability to shed excess leaves.
Deciding what kind of trees to plant and where requires forethought. Bastian recommends grouping trees away from grassy areas so that both can thrive without a lot of supplemental care.
Paying close attention to trees can have many payoffs. Healthy trees improve air quality and absorb water runoff. Three trees shading a well-insulated house can reduce annual cooling needs by 6.5 percent. In winter, they serve as windbreaks, lowering heating costs. And, of course, there’s no way to calculate the real worth of their grace and beauty.
For more information, call 312-427-4256 or 630-719-2424.
Susan DeGrane is the assistant editor of Conscious Choice.
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