What’s causing winter damage to the base of my trees and shrubs?

Q: I’ve noticed damage to the base of my trees and shrubs. What could be causing this?

A: Foraging animals, particularly rodents, often cause damage to the base of young tree trunks and shrubs. Rabbits and voles, in particular, eat the bark of young trees and shrubs, and squirrels can damage bark, leaves, and fruit by chewing.

Which plants are most often damaged by animal foraging?

Plants and trees that are commonly affected include:

• Flowering crabapple trees
• Ornamental cherry trees
• Burning bush 

However, animals can damage any kind of tree or shrub as they look for food and as the winter drags on, so some unlikely species can become damaged as well.

How can I identify animal damage on trees?

Look for scraping or bite marks at the base of trunks, especially on young trees. In some cases, the bark may have been stripped or removed from a section of the tree. This bark stripping can prevent the tree from spreading water and nutrients up into the tree canopy and can negatively impact the health of the tree. Additionally, any kind of damage to tree trunks can provide a place for disease or pests to enter the tree, further weakening it. 

Why do animals choose certain trees to chew on?

Animals are more likely to chew on trees if they’re hidden from predators (and humans). This protection can be from trees that are surrounded by ground cover, shrubs, or debris near their trunks. It can also come from deep snow (such as from drifting snow, plowing, or shoveling) that shelters the animals from view. 

Voles, in particular, create underground tunnels that are often not spotted until the snow melts in the spring. When voles are digging underground, they can damage the roots of trees, leading to further complications and issues with the trees’ health. 

How can I protect my trees from foraging animals?

You can keep rodents and other small animals away from your trees and shrubs by:

• Removing any groundcover or shrubs that are close to trees
• Ensuring no snow piles up at the base of trees and/or shrubs
• Wrapping the base of the trees or shrubs with 24-inch wide mesh or a plastic drain tile with one side sliced to slip over the trunk
• Setting traps to catch mice, gophers, or voles
• Encouraging natural predators such as hawks and owls

Is there anything I should not do?

At Bay Landscaping, we do NOT recommend:

• Using mothballs outdoors (not only are mothballs not approved for outdoor use, they can kill other animals, including pollinators, and can damage your plants)
• Using any kind of poison 
• Tilling the soil around the tree or shrub (this can harm the roots)
• Keeping wire mesh or plastic drain tile around your trees year-round. You should remove it come spring or you risk permanent damage to the tree.

For more on this topic, read this article from the Michigan State University Extension.