Hoyt Arboretum, Portland, Oregon, USA

Common name: cascara, buckthorn

Family: Rhamnaceae

Distribution: Northwest USA

Habitat: Moist soils in open areas, understory of coniferous and mixed evergreen forests

IUCN Red list: Least concern

Hardiness: Zone 3b -35 to -30 F

Life form: Deciduous tree

Usage: Ornamental shade tree

Comments: A deciduous shrub to small tree native to western North America from southern British Columbia south to central California, and inland to western Montana, growing to 15-30’ tall. Leaves, 2-6” long, 2” wide, simple, alternate, dark, glossy green, elliptical to oblong, with furrowed, parallel veins, clustered near the ends of twigs. Flowers are inconspicuous, with 5 greenish-yellow petals in umbel-shaped clusters. The fruits ripen to a purplish-black. The bitter bark is a smooth, silver gray.
Grown best in moist, well drained soils in part shade.