Garden Variety: Protect tree bark from occasional squirrel damage

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A squirrel peeks out of a hole in a tree. Squirrels can damage trees through extensive stripping of the bark.

Squirrels are generally good neighbors that occasionally become a nuisance by stripping bark from trees, snipping twigs, eating tomatoes, getting into bird feeders and participating in other minor but annoying activities. Stripping of bark from tree branches and trunks is especially problematic if wounds are large, and tree owners may wish to protect trees if this type of damage occurs.

Experts disagree about why squirrels sometimes strip bark from trees. Theories include wanting the bark for nesting material, sharpening their teeth, burning off extra energy, seeking calcium and seeking moisture and sugar from the cambium of the tree.

Squirrel damage can occur at any time during the growing season but most commonly occurs in the summer months. Damage might become evident with a pile of bark shavings under the tree or by noticing the wound itself high up in the tree.

A small amount of bark stripped from tree branches is little cause for concern. Healthy trees, especially established ones, will seal over the wound over time.

If the wounded area goes all the way around a branch, a process referred to as girdling, the branch will die back to that point. This is when trees suffer. Tree owners and caretakers may wish to prevent further damage.

If you notice extensive bark stripping in valuable trees, try feeding squirrels to deter stripping activity. In Kansas State University’s Urban Wildlife Damage Control publication on tree squirrels, Extension Wildlife Specialist Charles Lee recommends offering field corn (shelled or on cobs) near affected trees. Place corn on the ground or on a shallow feeding platform.

For smaller trees, wrap branches with metal sheeting or tree wrap, or use squirrel baffles, which are funnel-shaped wraps made to keep squirrels from climbing bird feeder poles.

In extreme cases, squirrels can be trapped in accordance with local ordinances. Remember that relocating them means moving the problem somewhere else, and that more squirrels will likely move in to the vacated space.

A research paper published in February 2016 titled “A novel causal mechanism for grey squirrel bark stripping: The Calcium Hypothesis” makes a case for squirrels seeking calcium in summer months. Calcium is present in the conductive tissues of the tree located just below the bark’s surface. More research is needed to support or disprove this claim.

There are two species of squirrels that reside in northeast Kansas. The most common is the fox squirrel. It is usually reddish-brown (like a fox) but may be several shades of brown, black or gray depending on parentage and time of year. The other species in the area is the gray squirrel. Grays squirrels are gray in color with a white underbody and white tip at the end of their tail. Gray squirrels are smaller than fox squirrels at maturity but are more aggressive.

Fox squirrels and gray squirrels are also differentiated by their habits. Fox squirrels enjoy city and country life equally and spend a fair amount of time on the ground. Gray squirrels prefer wooded areas and spend more time in the treetops than fox squirrels.

Other damage to trees and plants in the landscape and home garden is generally insignificant. Trees with clipped branches will seal over the wound with time. Half-eaten tomatoes are wasted but plants will produce more. Tulip bulbs that disappear can be re-planted. And despite the little nuisances they sometimes cause, squirrels can be fun to watch.

Fox squirrels that make it to maturity live 8-12 years in the wild, and gray squirrels live 12 years in the wild on average, so the ones you see each year are likely the same. Most squirrels die before adulthood though, thanks to cats, foxes, hawks, coyotes, automobiles and other perils.

— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation.


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