This Garden Column is being released early in order to make this information available. This is the column for the week of March 9, 2007, but can be used immediately.
By James Romer
Iowa State University Extension
A snow and ice covered landscape can be a winter wonderland. Unfortunately, heavy amounts of snow and ice accumulated on the branches of trees and shrubs in many parts of Iowa and have caused considerable damage. Multi-stemmed evergreens, such as junipers and arborvitae, along with weak-wooded deciduous trees, such as Siberian elm, green ash and silver maple, are most susceptible to branch breakage. Trying to shake or strip snow and ice from limbs and branches can increase the amount of damage to trees and shrubs.
Large branches or entire trees can be lost due to the tremendous weight of the ice. When the weight of ice causes a small tree to bend sharply, it may be possible to prop it up to prevent breakage. Don't attempt to remove the ice by beating the branches with a broom or rake. This will only cause greater damage.
Accumulations of heavy, wet snow on evergreens can also cause severe branch breakage. When shoveling, don't throw heavy, wet snow or ice onto shrubs or small trees. The weight of the heavy, wet snow and ice can cause additional considerable damage. Individuals should stay away from large, ice-laden trees. Nothing can be done to prevent damage to large trees. Individuals, however, can be severely injured or killed if a large tree or branch suddenly crashes to the ground while someone is underneath it.
If your tree has been damaged, carefully examine the extent of damage. Give immediate attention to trees that are hazards to people or property. If a power line is involved, utility company personnel are the only ones who should be working in the area. After the elimination of hazardous situations, individual tree care can be assessed. Unfortunately, assessment is a judgment call with a large gray area. Severe splitting of the main trunk or an injury that removes more than one-third of the bark around the tree is a wound that few trees can survive.
Broken treetops also are severe injuries. Repair methods are geared toward assisting the tree recover as quickly as possible. Most repair work involves pruning. If branches break on a tree, prune the damaged limb back to the main branch or trunk. When removing larger limbs (usually those with a diameter exceeding 1 inch), a three-cut technique should be used to prevent the branch from tearing away as it is being removed.
The initial cut is made on the underside of the branch, 6 to 12 inches from the trunk, about one-third to one-half of the way through the limb. The second cut is made on the top of the branch, 1 inch further out. As the second cut is made, the weight of the branch will cause it to break at the pivot point between the two cuts. Once the branch falls, the third and final cut is made outside the branch collar.
Wound dressings are not recommended. Cabling and bracing may be appropriate if the cost involved can be justified. This method of repair does not save trees with extensive structural damage. Damaged shrubs may need to be pruned in the spring to restore their attractive, natural shape.
After deciding the treatment necessary, the next decision is who will do the work. Many of us do the work ourselves or hire a tree care specialist. For minor damage on small trees a homeowner with knowledge of proper pruning procedures, access to proper equipment and desire can handle the job. Severe damage is better left to someone who specializes in this area particularly with large trees and when work must be done high off the ground.
When contracting repair work, both the homeowner and the tree service professional must clearly understand the work to be done and the cost involved. If your area has received considerable damage, repair professionals may be heavily booked. It may take some time before they can get to your site. It is important to keep people away from potentially dangerous situations until the necessary work is completed.
If tree replacement ends up being your only alternative, select tree species and cultivars with a sturdy reputation. Excellent maple selections include black and sugar. Oak species include white, swamp white, bur, and red. Linden (both American and littleleaf), thornless honeylocust and ginkgo are other possibilities.
Three ISU Extension publications are available to help homeowners. They include:
These can be ordered through any ISU Extension county office, online at https://www.extension.iastate.edu/store/ or by calling the ISU Extension Distribution Center at (515) 294-5247.