Image © Paul Wray, Iowa State University, Bugwood.org
Common and glossy buckthorn (Rhamnus cathartica and Rhamnus frangula) originated in Eurasia as ornamental shrubs.
Both have purple-black fruits and oval or oblong dark green leaves. Both can reach 20 feet tall.
Common buckthorn is found in disturbed forests and abandoned fields and along roadsides, fencerows and the edges of prairies. Glossy buckthorn is found in wetlands, sedge meadows and mesic uplands. Both are spread by birds that eat the fruits, which are strong laxatives, and disperse the seeds.
Because buckthorn grows quickly, it robs soils of moisture and nutrients. The resulting bare soil is susceptible to erosion and is uninhabitable by most wildlife. Buckthorn also spreads quickly and is one of the first plants to leaf out in the spring and one of the last ones to drop its leaves in the fall. These factors allow it to create low, dense canopies that prevent sunlight from reaching native shrubs, young trees, wildflowers and other groundcover below. This allows buckthorn to effectively smother native vegetation.
Buckthorn roots are shallow, so gardeners can dig out or pull small to medium-sized plants, preferably in spring when the soil is moist.
Research findings released May 1, 2013 by Lincoln Park Zoo and Northern Illinois University concluded that invasive European buckthorn, common in the DuPage County area, contributes to amphibian decline and altered mammal distribution throughout the Midwest.