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Oklahoma State University

Mechanical injury to trees can cause irreversible damage

Wednesday, July 8, 2020

It is important to be careful when mowing and weed trimming around the trunks of trees. Mechanical injury to the bark can cause irreparable damage.

On a hot summer day, spending the afternoon bathed in the shade of a tree is a great escape from the heat. While homeowners do their best to make the landscape an inviting space, some of the needed equipment to do so could put those trees in jeopardy.

David Hillock, Oklahoma State University Extension consumer horticulturist, said trees are an important aspect of any landscape.

“Trees add a lot of dimension, texture and color to your landscape and can be a significant investment. When taken care of properly, these trees can add value to your property,” Hillock said. “Keeping them healthy through proper management and care ensures they’ll be around for the next generation of your family. Unfortunately, one of the most common stresses to urban trees is caused by humans, and one that easily can be avoided.”

The trunk of a tree not only provides support to the branches and leaves, it is the main conduit for water and nutrients up and down the tree between the leaves and root system. The cambium layer, which lies just below the bark, is a thin area responsible for this movement. If damaged, Hillock said the movement of this vital solution up and down the tree is hindered.

“Now that we’re in the height of summer, the lawnmower and weed eater are likely getting a good workout. However, if you’re not careful, you can easily damage your trees with these pieces of lawncare equipment,” he said.

This man-made stress often is referred to as lawnmower or string trimmer blight – mechanical injury to the trunk of the tree by careless use of equipment near the trunk. This injury usually results in wounds that could eventually be fatal to a tree, depending on severity of the damage and how often it occurs.

Hillock said minor damage on one side of the trunk may result in only a few stressed branches; however, if the damage surrounds the entire trunk, the tree can be sent into a slow decline. This sort of damage is enhanced when the tree is then further stressed by environmental conditions such as drought and extreme heat.

“The physical damage, coupled with harsh environmental conditions, can make it difficult to recover from and return to normal growth,” Hillock said.

The best way to address this issue and not cause damage to your investment in the landscape is to not grow grass under the tree, or at least not right up to the base of the tree. Hillock said keeping the area around the base of the tree free of grass and weeds means mowing and trimming equipment can be kept as a safe distance from the tree.

Tree guards can be used on young trees to help protect the trunk, but it is still recommended to maintain a grass/weed-free area around the tree so homeowners will not have to get the equipment too close.

“Trees are so important in a landscape and taking proper care of them helps ensure the trees will be around for generations to come,” Hillock said.

MEDIA CONTACT: Trisha Gedon | Agricultural Communications Services | 405-744-3625 | trisha.gedon@okstate.edu

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