Why is Freezing Rain So Tough on Trees?

We are all familiar with damage that a severe thunderstorm or tornado can cause. Summer wind events can cause massive damage to trees. The force of wind causes breakage when the strain of wind loads push it past the limit for a tree or branch.  

In dormant season, once leaves drop, much of a tree’s additional weight from its leaves is lost. However, winter can still present threats to a tree. Big snow events grab the winter weather news. Light and fluffy snow presents little damage threat to trees because it usually falls or gets blown away. On the other hand, ice easily accumulates on surfaces like trees and power lines. With the added concentrated weight of the ice, tree branches and power lines can snap. Just a 1/2-inch accumulation on power lines can add 500 pounds of extra weight. Wind only adds to the ice load causing trees to break sooner and more easily.   

Ice loading is made worse with fine-textured trees, such as river birch and lace bark elm (lace bark elm often has fruit toward the branch’s ends that act as points for ice to start its build-up). Some species, like hawthorn and honeylocust, are brittle and less adept at bowing down with increased stress of ice loads. Ice loads toward the ends of branches exacerbate the stress on a tree. Freezing rain is a deceiving and destructive winter precipitation. If ice accumulates and loads onto objects such as trees, conditions can change quickly from a photogenic glaze that trims the twigs into something that is damaging and catastrophic for the tree, causing its breakage and failure. 

Arborists recommend against forcing trees back into position. Take a few pictures of the pretty ice glaze on your tree branches and pray for warmer temperatures (and calm winds) in days to come. 

The Ohio Department of Natural Resources (ODNR) has tree tips for residents to deal with freezing rain on their trees. 

Below are a few considerations for those dealing with ice-damaged trees.  

• Don’t be too eager to force trees and shrubs bent over by ice into their former upright position. In removing the ice, you may damage the plant. Wait for warmer weather to melt away the additional weight. If the lean was less than 45 degrees, the plant should right itself, but some staking may be required. 
• Thick ice accumulation on larger trees will often exploit dead branches, those weakened by decay, and those poorly attached to the main stem. Topped trees are particularly vulnerable to ice damage due to this destructive practice. Some trees, because of their growth and form, are more susceptible to ice accumulation than others, and are thereby normally prone to damage. 
• For larger damaged trees, always seek the advice of a Certified Arborist. They know how to safely work around trees, and what treatments are and are not warranted.  

Stay safe and keep an eye on your trees!

Written by: Cincinnati Parks Urban Forestry Department
Source: https://ohiodnr.gov/wps/portal/gov/odnr/