Buckthorn (Rhamnus cathartica) is a non-native, fast-growing, deciduous shrub. Often used as a hedge plant, the shrub is so hardy that it is considered an invasive plant by most states. In addition, the plant does not have any natural enemies, according to the Minnesota Department of Natural Resources, and in fact often hosts fungal diseases that can seriously affect other, native plants in America.
The native habitat of buckthorn is the deciduous forests of Europe, western Asia, and the northwest corner of Africa. The plant was introduced to the United States in the early- to mid-1800's and widely used as a landscape shrub. Home gardeners found the early leafing habit and black drupes to be very attractive, and the plant quickly became popular.
Common buckthorn is very common in the United States. In fact, the habitat of the buckthorn in the United States is both widespread and varied, especially in the eastern part of the country. This plant is so hardy that it grows almost anywhere. Buckthorn can be found in both urban and rural areas, in street medians and formal parks, and in woodlands and forests.
Buckthorn grows best in habitats that receive full sun, according to the University of Connecticut. These plants can tolerate a wide range of soil conditions, from sandy to clay, and are highly adaptable even to adverse conditions such as pollution. They are also easy to transplant.
Although not native to America, buckthorn has become naturalized in the country and can now repopulate itself easily. The plant drops an enormous amount of seeds into its immediate habitat; as much as 75 seeds per square foot, according to the Minnesota Department of Natural Resources. In addition, birds and other animals love the drupes, consuming them in large quantities and ensuring that the plant spreads.
Buckthorn produces leaves earlier than most native plants in America, creating early, dense shade that can block sunlight from reaching other, desirable plants. In this way, it crowds other plants out of its habitat and can overtake a home garden, woodland area, and even parks and other public venues. For these reasons, many states have declared buckthorn to be an undesirable, invasive weed.