Common buckhorn arrived here from Europe in the mid-nineteenth century to be used as a hedge. Lacking natural controls from insects or disease, it forces out native plants, forming impenetrable layers of vegetation especially in poorly-drained areas and along waterways. There are native species of buckthorn, but they do not force out other plants.
Buckthorn is a tall shrub or small tree, growing up to 25 feet high, often sporting multiple stems at its base. The bark is similar to that of a cherry tree, with egg-shaped, glossy leaves that stay green late into the fall, later than most plants. Berry-like clusters of fruit ripen in August and September.
One of the more troubling aspects of common buckthorn is that it serves as an overwintering host to the eggs of yet another invasive species, the soybean aphid. These aphids suck the nutrients from soybean plants, potentially causing significant damage to one of Ohio’s most important crops. The soybean aphid arrived in the Midwest from the Orient in 2000 and is now our most important insect pest of soybeans. If the buckthorn had not already been in the USA, the aphid never would have become established.
A final irony is that yet another invasive species, the multicolored Asian lady beetle, is a voracious predator of soybean aphids, and researchers at Michigan State and other places credit the lady beetle for partial control of the soybean aphid in recent years. This may not be appreciated by those of us who are subjected to home invasions by lady beetles in the fall.
If you discover buckthorn on your property, remove it by cutting it at soil level and treating the stump with an approved herbicide.
Dave Horn provided entomological input for this article.