Bark — it’s not just for beavers

Looking out the kitchen window I can see a grove of English elm trees. They were planted many years ago by my neighbor and have become a stately group of large trees with a nice shape. Their crowns provide excellent shade in the summer and they seldom are damaged by storms.

At this time of year, however, a strange color can be seen on several branches. A bright whitish yellow is visible on some of the smaller branches. Walking up and looking more closely at these branches, I can see that the yellow is actually the bare elm wood that is exposed. The bark has been stripped from the branches and small hash marks are visible on the wood. Looking up I can also see strange clumps of leaves that look like bird nests high up in the trees.

Well worn trails in the grass between the trees make it clear that some creatures have been running back and forth between the trees. Yup it’s our old friends the squirrels, they must be getting hungry this time of year. Fortunately for these elm trees the damage doesn’t seem to be too bad, but that’s not always the case.

As arborists in Colorado, we commonly get calls about, “Something Eating My Tree” in the winter. Typically this type of bark stripping damage is caused by hungry squirrels who have run out of other food sources. The inner bark of many trees contains nutrients and starches which provide sustenance. Unfortunately, these “tree rats” as some angry people refer to them can cause severe damage to trees. It’s even possible for squirrels to kill off whole canopies of smaller trees.

Squirrels aren’t the only bark-eating animal in Colorado. Voles, also known as field mice, often turn to feeding on roots and the bark of trees and shrubs during the winter months. Unfortunately, the damage caused by voles is often invisible, because it takes place under thick ground cover, under snow, or at the base of thick shrubs like juniper.

The damage doesn’t show up until the spring when temperatures rise and the water conducting cells, or xylem, in the tree has been severed. The interconnecting trails of voles are often visible in the lawn after a snow melt. It isn’t uncommon for vole damage to kill new trees and shrubs, so having these plants inspected is a good way to avoid this type of injury.

Now before we go judging squirrels and voles, it’s important to remember that they aren’t the only ones on this planet that rely on tree bark as a form of sustenance. In fact there is a long history of other animals, including humans, that rely on the nutritious inner bark of trees.

The word Adirondack refers to a tribe of Algonquin Native Americans, and now a region of the U.S. Translated it means “bark eater” or “tree eater.” Most of us haven’t experienced the type of hunger that would drive us to eat bark, but that doesn’t mean that we should overlook the multitude of other uses of bark.

Perhaps you are about to kickback and pour yourself a nice glass of wine while reading this article. Chances are that cork is made from the bark of a cork oak tree. Or you might throw on a pair of gloves to wash the dishes made from natural latex, a fluid that is found below the bark of rubber trees. And don’t forget salicin, the precursor to aspirin, which is made from the inner bark of willow trees and was commonly used for headaches and fevers. Hopefully it won’t be needed after reading this article.