Rhamnus purshiana

The cascara or cascara buckthorn in the Rhamnaceae family is native to western North America from southern British Columbia south to central California, and eastward to northwestern Montana. It is a small tree up to 10 m tall.

The dried bark of cascara has been used for centuries as a laxative, first by Native Americans in the Pacific Northwest, and then by European settlers.

• Leaves are simple, deciduous, alternate, clustered near the ends of twigs. They are oval, 5–15 cm long and 2–5 cm across, with up to a 2 cm long petiole. Veins curve upward toward the end of the leaf.
• Flowers are tiny (4–5 mm in diameter) with greenish yellow petals, in clusters on the end of stems.
• Fruit is a round drupe 6–10 cm in diameter, first bright red and turning deep purple or black.