An evergreen bush, ultimately 10 or 15 ft high; young shoots downy the first season. Leaves oblong or oval, mostly rounded at the base, rounded or broadly pointed at the apex, minutely or not at all toothed, 1 to 4 in. long, about half as wide, glabrous above, downy on the veins beneath, veins parallel, usually in eight to twelve pairs; stalk 1⁄6 to 5⁄8 in. long, downy at first, glabrous the second season. Flowers in downy, short-stalked umbels. Fruits 1⁄4 in. across, dark purple, globose.
Native of western N. America, from Oregon southwards. With some affinity to R. purshiana in the stalked flower-clusters, this is easily distinguished by its dwarfer, purely shrubby habit, its evergreen foliage, and more globose fruits.
var. oleifolia Hook. – This has smaller, narrower leaves, oblong-ovate, 11⁄4 to 21⁄2 in. long, 1⁄2 to 1 in. wide, uniformly toothed. There are, no doubt, forms intermediate between this and the type.
subsp. tomentella (Benth.) C. B. Wolf R. tomentella Benth.; R. californica var. tomentella (Benth.) Brewer & Watson – A very distinct form, the undersurface of the leaves being covered with a close, velvety, yellowish or greyish felt; young shoots and leaf-stalks the same.
Other subspecies are described by C. B. Wolf in Rancho Santa Ana Bot. Gard. Mon., Vol. 1 (1938), pp. 64-70.
All these buckthorns are interesting evergreens, and have in their bark aperient properties identical with those alluded to under R. purshiana; they help to meet the demand for the Cascara Sagrada drug (see R. purshiana).