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| Ice breaker (December 2005) |
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Proper tree selection and regular pruning reduces ice-storm damage
By Larry Reichenberger
The coating of ice often left by winter storms can turn an ordinary landscape into a glistening wonderland. However, ice storms can also leave a ghastly wasteland with broken trees, damaged homes, and downed power lines. The final outcome may depend on something as simple as the tree planting and pruning decisions made by property owners.
Ice storms occur when rain falls from a warm air mass that has overridden cold air near the surface. With temperatures below freezing, the ice accumulates on contact with any cold surface, including tree branches. Even tiny branches can grow to an inch or more in diameter and it’s not uncommon for this accumulation of ice to increase the weight of a tree by up to 30 times. Tree species that have poor limb structure, damaged branches, or haven’t been pruned, often fail under the load and crash to the ground.
Select strong trees
In January 2005, a record-setting ice storm hit south central Kansas and became the state’s most expensive natural disaster. During the cleanup, Kansas State University horticulturist Bob Neier surveyed the damaged trees and found that species, age, health, and past care had an effect. “The most extensive damage was to Siberian elms - they accounted for up to 80% of the loss,” says Neier. “Other popular tree species that suffered heavily were the Bradford pear, Russian olive, and willow.”
Neier adds that no tree species came through the storm without damage, but some types proved to be “strong” while others were “weak.” These types are included in the list below, which was developed by tree-health specialists at the University of Illinois. “Trees that have many fine-textured branches, that retain dead leaves, or that have a narrow ‘V-shaped’ branch angle where the branches grow close to the trunk, are easily damaged. By contrast, deciduous trees with a wide branch angle that approaches 90 degrees straight out are strongest,” says Neier. “Some tree species are genetically prone to forming ‘included bark,’” says University of Illinois tree specialist Jeffrey Dawson. “This means bark is trapped in the branch junction and the result is a weak connection.”
Pruning adds strength
Regular pruning can also help trees survive an ice storm. “As the tree is growing, any branches that form with a narrow angle should be cut out,” Neier says. “Also, branches that are damaged, and any that rub, should be removed. This will thin the interior of the tree and train it to develop strong branch angles.” Dawson says ice-storm resistance isn’t the only factor to consider. “The weak trees have other benefits, but their number should be limited in the landscape.”
List compiled at the University of Illinois
Strong trees
Linden (silver and littleleaf),Oak (white, red, bur, and shingle),Pear (aristocrat and chanticleer), Redbud, Sweet gum, London planetree, Catalpa, Ginkgo, Kentucky coffee tree, Bald cypress, Maple (red, sugar, amur and Norway), Black walnut, Golden rain tree, Honey locust, Chinese pistache.
Weak trees
Elm (Siberian and American), Bradford pear, Willow, Austree, Russian olive, Green ash, Silver maple, Pin oak, American linden, Hackberry.
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