It’s hard to believe on a gray winter day when trees are bare, but in just six or eight weeks the first of them will begin to open their leaves.
Before spring arrives, take the time to examine your trees’ bark and branches for signs of damage, says Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle. “Problems are easier to spot right now than they will be when the tree is full of leaves,” she said.
If you see an issue on a small tree, you may be able to deal with it yourself, often by pruning. “As long as you can do the work with your feet on the ground, you can probably handle it,” Yiesla said.
For larger trees, call in a professional arborist who has been trained to diagnose problems and propose solutions.
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“If a problem calls for pruning a larger tree, leave that to the professionals,” Yiesla said. “It can be extremely dangerous.” Working above the ground on tree branches that may weigh hundreds of pounds requires special safety training and equipment. For advice on choosing an arborist, see mortonarb.org/choose-arborist.
Here are some issues to look for when you examine your trees:
Cracks. A major crack in a tree’s bark, whether on the trunk or branches, can weaken the wood, permit rot or allow diseases and pests to enter. On small trees with thin bark, cracks that run lengthwise up the trunk may be caused by quick fluctuations in temperature, such as a bitterly cold night followed by a sunny, warm day.
If a new crack is not too severe, a young tree may eventually be able to seal it over with bark. However, if you see a crack that looks old and is still open, examine it closely for signs that rot or disease has set in. “If the wood feels soft, it’s rotting,” Yiesla said.
There’s nothing you can do to fix a crack. The Arboretum does not recommend trying to seal it with pruning paint or wound-sealing products, which do not help the tree heal. Coating a crack can trap moisture, which then encourages disease. “You just have to wait and see if the tree can seal the crack on its own,” she said.
If you see cracks in the trunk or large branches of a large, older tree, call in an arborist to make sure the wood is still structurally sound or, if it is unstable, to remove it.
Dead wood. It’s normal for some branches to die on a tree over time. Often, for example, lower branches that are shaded and deprived of sunlight will die off. “In the forest, it’s not a problem when a dead branch drops off,” Yiesla said. “But in our yards, large falling branches are a potential hazard.”
How can you tell if wood is dead? A live branch will have young twigs, often with visible buds, especially toward the branch tip. If you can reach the branch, you’ll be able to feel that the twigs are flexible and springy. If you make a small nick in the bark, you usually will be able to see the green layer of growing cells just beneath it.
A dead branch will have few or no twigs. The wood will be dry and brittle. Areas of the bark may peel off, exposing bare wood.
“If you can do it safely, prune out dead branches,” Yiesla said. On larger trees, have a professional do it.
Cankers. When a wound in a tree’s bark is infected by a disease-causing fungi or bacteria, it can cause a damaged area called a canker. Sometimes the canker is an area of swollen bark, and some cankers bleed sap. An area of discolored bark may be an indication that a canker is growing beneath it, and eventually the bark may fall off. You can learn more at mortonarb.org/canker-diseases.
Trees commonly infected with canker diseases include spruces, pines, poplars, willows, junipers, Russian olives, Douglas firs, arborvitaes, honey-locusts, oaks and maples.
“If you see an area of bark that doesn’t look right, get it checked out,” Yiesla said. The Plant Clinic may be able to help you identify the problem.
For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or [email protected]). Beth Botts is a staff writer at the Arboretum.