Much ado is made about common buckthorn in Wisconsin, throughout the Midwest and the East as one of the most noxious of invasive shrubs / small trees. Unfortunately, glossy buckthorn often gets overlooked in lieu of its more famous cousin, though glossy buckthorn is also highly invasive and must be checked if it is found on your property.
Common buckthorn and glossy buckthorn are closely related species originating in Eurasia and introduced to North America as ornamentals. They were planted in Wisconsin as early as 1849, becoming widespread after 1900. They are currently naturalized throughout southern Canada and the northeast U.S. They are well established and rapidly spreading in Wisconsin, predominately via birds.
Glossy buckthorn is "restricted" by the state of Wisconsin, meaning this non-native species is very detrimental but found to be too widespread in Wisconsin to realistically expect to eradicate or contain it. The goal for such a species is to slow their spread. It is illegal for people to transport, import, transfer, sell and introduce species on the restricted category. It is not illegal to possess restricted species but, if an invasive species is just starting to spread on your land, you are encouraged to try to control it to keep it from spreading.
Glossy buckthorn has thin, glossy, ovate or elliptic leaves. The upper leaf surface is shiny; the lower surface can be hairy or smooth and their margins are entire (not toothed).
Glossy buckthorn is a deciduous perennial shrub or small tree that reaches up to 23 feet in height. It has alternate, glossy leaves that are oval or elliptical. They are smooth or slightly hairy, thin and from one to three inches long. Its brown-green branches have elongated sentinels, which are slightly raised on the surface of the bark. Glossy buckthorn flowers are yellowish-green, have five parts, and are perfect flowers arranged in umbels, which resemble the spokes in an umbrella. Buckthorn establishes dense stands, choking out native shrubs and herbaceous plants.
Preferred habitat: Glossy buckthorn occurs in a variety of habitats, including woodland borders and wet areas that are typically open and sunny. Often, the soil is fairly acidic.
Distribution: In North America, glossy buckthorn occurs from Nova Scotia to Manitoba, south to Minnesota, Illinois, New Jersey and Tennessee.
Information courtesy the Nature Conservancy Connecticut Chapter and the Wisconsin Department of Natural Resources.