Cascara buckthorn Rhamnaceae Frangula
purshiana (DC.) A. Gray
Leaf: Alternate, simple, deciduous, oblong to elliptical, 2 to 6 inches long, dark glossy green above and paler below, prominently penniveined, margins wavy or finely serrate.
Flower: Species is monoecious; with either perfect flowers or imperfect flowers on the same plant, inconspicuous, small and greenish-white in loose clusters.
Fruit: A small (1/4 to 1/2 inch diameter), round, black drupe with a yellowish inner pulp, not edible (has laxative properties).
Twig: Young twigs are slender and moderately stout, reddish brown and pubescent; older branches are smooth and reddish brown to gray; buds are naked (without scales) and covered with rusty tomentum.
Bark: Thin and grayish brown, often mottled with white patches of lichens; inner bark is yellow, tastes bitter, and has laxative properties.
Form: Can grow as a tree to 50 feet tall and 10 to 20 inches in diameter or as an erect shrub with multiple stems to 15 feet.
Looks like: California buckthorn - common buckthorn - red alder