Buckthorn (Rhamnus) is an invasive species originally from Europe. Invasive species are "[i]nvasive species are plants, animals, or pathogens that are non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause harm" (invasivespeciesinfo.org). That being said, buckthorn is threatening in Minnesota. Buckthorn out-competes native plants, threatens the future of forests, creates erosion by shading out native plants on the forest floor, hosts fungus, forms vegetation layers, and since its invasive, it lacks natural enemies. In order to rid of buckhorn you must cut it down and then chemically treat the stumps. It is illegal in Minnesota to buy, sell, or intentionally grow buckthorn. Buckthorn is an altogether harmful plant to the environment. Do not buy or sell buckthorn! Stop its growth and kill/treat it if possible!