Buckthorn
Buckthorn, one of a large group of trees or shrubs, most of which are native to north temperate regions. The common buckthorn, native to Eurasia, is found throughout the United States, sometimes cultivated as a hedge plant. It is a shrub, growing 10 to 25 feet (3 to 8 m) high. It has oval leaves with finely toothed edges, twigs that terminate in thorny spines, yellowish-green flowers, and blue-black berries.
Another common species in the United States is the cascara buckthorn. Cascara Buckthorn.)
The common buckthorn is Rhamnus cathartica of the buckthorn family, Rhamnaceae.