There are two types of invasive buckthorn in Minnesota. Common buckthorn is easily found in late fall when many native shrubs and trees have lost their leaves. Common buckthorn will often have green leaves through November. Glossy buckthorn does not stay green as late as common buckthorn. Use caution as many native trees look similar to buckthorn, and some native trees hold their leaves into the winter.
Buckthorn plants 2 inches in diameter or larger can be controlled by cutting the stem at the soil surface and treating the stump with herbicide or covering the stump to prevent re-sprouting. Cutting can be done effectively with hand tools, chain saws or brush cutters. Stumps should be treated immediately after cutting (within two hours) with an herbicide containing triclopyr (found in many brush killers, Garlon 3A or 4) or glyphosate (Roundup and others) to prevent re-sprouting. An alternative if only cutting a few stumps is to cover them with a tin can or black plastic to prevent re-sprouting. For smaller plants, pulling or herbicide application are methods for control.
Laura Van Riper, DNR terrestrial invasive species coordinator