Cascara Buckthorn, a shrub or small tree that grows in the Pacific Northwest of North America. It reaches a height of about 30 feet (9 m). The plant has large, elliptical leaves and small, greenish flowers. Its round, berrylike fruits become black when mature. The tree is grown commercially for its bark, which yields the drug cascara sagrada, used as a laxative.
The cascara buckthorn is Rhamnus purshiana of the family Rhamnaceae.