What Animal Is Damaging My Tree’s Bark?

Question

We’ve had a Norway maple in our back yard for over 15 years. This summer, we observed that the bark had been removed by an animal. In our area, there are raccoons, skunks, groundhogs and stray cats. We don’t have any pets. What animal is attacking our tree and what can we do to stop it?

Carlos Valladares

Answer

In fact, the only animal that can be blamed for the damage to your tree is a human being. Because the wound at its base visible in your photo is due not to the ravages of a four-legged animal, but rather to a lawn mower, a weed trimmer or other power tool banging up against the tree’s bark.

Probably the original damage occurred years ago, even more than a decade, when the tree was still young and its bark was thin and easily damaged. When a power tool hits a tree’s bark, especially repeatedly, it leaves a wound much like a bruise, with some swelling. However, that’s out of sight under the outer bark and goes unnoticed. Thus, the outer bark is pushed free of the inner back, but only years later does it split open to reveal the damage this kind of wound causes.

However, it is possible that a small animal, such as a chipmunk or a vole, saw a space under the bark and removed a few chunks of it so that it could create a shelter. (That would actually benefit the tree, as it would increase air circulation.) I suspect, though, that the damage has been visible for years, but you just hadn’t noticed until now. Even a cursory look shows the real damage is far from fresh: it occurred many years ago!

What Should You Do?

The only thing you can do is carefully cut away any loose bark that remains to expose the wound to the outside air and thus improve air circulation. This could reduce the risk of saprophytic fungi moving into the wood. In particular, avoid applying pruning paint or paste to the wound, as these products can trap moisture on it and lead to rot. Just leave the wound exposed to the open air.

It’s not impossible that even such an old wound as this one gradually heals over time. If so, fresh bark will form and start to cover the bare trunk.

The Next Time

If you plant a tree in a lawn in the future, install a barrier around the trunk to protect its bark. There are trunk guards that you can buy at any garden center or you can make your own trunk guard from a drainage pipe split along one side that you can place around the trunk. That way, the lawn mower or weed trimmer will bang into the tree guard, not into the living bark. As a result, the tree won’t be damaged.

Another possibility would be to surround the young tree with a circle of mulch. Since no lawn will grow near the trunk, that will eliminate any need to mow at the tree’s base.

If you hire a lawn care company, insist that they protect your tree when they mow. I regularly see their employees causing serious damage to trees with their lawn mowers and trimmers. Apparently, they’re being paid to mow fast, not well. Tell them you’ll bill them for any damage caused to your tree and they’ll quickly acquiesce.