Buckthorn is a nasty plant that is taking over woodlands, wetlands, prairies and other natural habitats. You may have some growing in your own yard and not know it.
Buckthorn was introduced to the United States in the 1800s as a tough, hardy landscape shrub. That toughness resulted in it becoming aggressively invasive to the point where it out competes native plants for nutrients, light, and moisture, degrades wildlife habitat, contributes to erosion, and forms an impenetrable layer of vegetation that crowds out woodland wildflowers and young maple, oak, ash and hickory seedlings necessary to regenerate the forest.
Buckthorn is easiest to identify in late fall; it is the only tree or shrub still holding onto its green leaves. Common buckthorn leaves are dark, dull to glossy green and rounded to egg-shaped with finely toothed margins. Glossy buckthorn has dark green, glossy, oval-shaped leaves. Bark is dark gray to brown and there are often sharp thorns protruding from both the trunk and branches. A good way to make a positive identification of either species is to scratch the surface of a trunk or stem. If you find orange inner bark, it is buckthorn.
Both species grow 10-25 feet tall and may be either trees or shrubs. In fall, berries turn black and are much loved by birds throughout the winter. Each berry contains 2-4 seeds that are poisonous to humans. The berries have a laxative effect on birds which ensures the spread of the seeds throughout the habitat. Seeds are viable up to five years so thousands of buckthorn seedlings can sprout from the berries of one mature tree.
Look closely at the woody shrubs in your yard. Are there a couple stems in the middle still holding green leaves? That is buckthorn and you need to get it out of there. If you can’t pull it, cut it and carefully brush the cut with a brush-killing herbicide.
Cutting buckthorn trees or shrubs without the herbicide follow-up is worse than not cutting them at all since they will re-sprout heavily with more branches than before. The best time of year to treat buckthorn with herbicide is late fall when the sap is flowing toward the roots.
A new, non-herbicide buckthorn control method is available thanks to UW-Madison engineering student Matt Hamilton. After a childhood spent pulling buckthorn on his family’s property, he knew there had to be a better way. He developed the Buckthorn Baggie, a black plastic bag that is placed over a buckthorn stump cut at 6” high. The bag spreads covers the cut stump and spreads out over the root flare and is zip-tied in place at 3” high. It is left in place for several months to a year until the buckthorn tree is entirely dead.
While pulling young buckthorn is easiest done after a soaking rain and herbicide application is best done in autumn, the Buckthorn Baggie method is effective year round.
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