After an ice storm, are some types of trees more likely to be damaged?

NASHVILLE, Tenn. (WKRN) - After a recent round of wintry weather, some Tennesseans woke up to find their trees coated in a sheet of ice, begging the question, “Are some trees more susceptible to ice damage than others?”

In fact, there are several types of trees you might be more likely to find bent to the ground after an ice storm. Some trees may also be uprooted or suffer massive crown loss as branches are broken by the weight of ice or snow.

"This is distinct from the freeze damage we saw over Christmas weekend. Plants aren't getting too cold, and tissue is not freezing to death. You're worried about the ice making the leaves and branches too heavy and causing mechanical damage as the limbs break off,” said Peter Grimaldi, Vice President of Gardens and Facilities at Nashville’s Cheekwood Gardens and Estate.

According to the University of Tennessee Agricultural Extension Service, there are at least 14 species of trees that are more susceptible to storm and ice damage than others, and just about as many that are resistant to damage.

Common species of trees found in Tennessee that might suffer more damage are beech, black cherry, hackberry, river birch, Virginia pine and boxelder. Other highly susceptible species are basswood, black locust, Bradford pear, crabapple, elm, magnolia, silver maple and willow.

Factors such as crown architecture, branch strength, brittle wood and areas weakened or injured by disease or decay can all impact the resistance of trees to storm damage, according to the University of Tennessee.

Species like magnolia and pine oak that keep their leaves in the winter are also particularly susceptible to damage from the type of winter weather seen this week, Grimaldi said.

“Simply due to the fact that evergreen trees retain their foliage throughout the winter and so there's more surface area on which to form ice, which gets heavy and breaks branches,” he said.

The brittle wood on willow, silver maple, boxelder, Brandford pear, elm and hackberry trees also tends to make them more prone to damage. At Cheeckwood Gardens and Estate, Grimaldi said he noticed some boxwood trees yielding to the ice this week.

The Leyland cypress, a common plant in domestic settings, also is known to be weak to ice.

"Those plants are also somewhat known as weaker wooded,” Grimaldi said. “You're looking at both broadleaf evergreens and needled evergreens with open branching patterns, maybe more horizontal branching patterns that might be affected by the ice."

Trees with fewer and thicker branches such as species of walnut, ginkgo, Kentucky coffeetree and white oak tend to come out of storms with less damage, according to the University of Tennessee. An upright and narrow crown also helps certain trees resist ice damage.

Larger, more mature trees are more susceptible to severe damage like a split in the main stem or trunk. While younger trees are more likely to bend during ice storms.

Loss of large portions of the crown, or top branches, results in tree stress and reduction in growth, according to the University of Tennessee. It also creates entry sites for insects and disease.

“The mode of damage is similar to storm damage in the summer, violent winds, summer thunderstorms,” Grimaldi said. “It's just different means of breaking that branch."

Depending on the degree of damage, some trees will recover on their own, while others need immediate care to repair the damage, and some are so severely damaged they will eventually die.

Broken branches generally do not affect tree survival unless more than 50% of the crown is involved, according to the University of Tennessee. However, if storm damage does occur, quick action is necessary to assess the damage and initiate care.

Homeowners can help repair damage by pruning smaller branches back to the point where they join larger ones. Large branches that are broken should not be cut back to the trunk.

"Ice is tricky because it forms around it and envelopes the leaves and stems,” Grimaldi said. "If a branch breaks you need to cut it back to either the primary stem or the next available node or branch angle and make a clean horticultural cut.”

Future storm or ice damage to trees can also be minimized through proper care as healthy trees are more adaptable to changes in the environment and react more effectively to damage. That includes watering, proper fertilization, annual pruning and protection from soil compaction.