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Idaho Mountain Wildflowers

Buckthorn Family, Rhamnaceae

The buckthorn family is made up worldwide of 58 genera and 875 species. Most are tropical shrubs or small trees, although it is represented in Idaho by plants belonging to two genera, Rhamnus and Frangula. All of the Rhamnaceae have bark that acts as a potent purgative. Other than the occasional use of our plants as ornamental shrubs, the purgative value of Frangula purshiana bark (cascara, described below) makes it the only American member of the family to have commercial value. Elsewhere the bark and berries of various buckthorns have supplied dyes used in painting and for textiles. The word rhamnus from which the family name was derived is an ancient term used for a now unknown species of thorny shrub or tree.

	Tobacco brush, Ceanothus velutinus Douglas ex Hook. (right) is common in our mountains. Other common names include “mountain-balm,” “sticky laurel,” “buckbrush,” “greasewood,” and just plain “ceanothus.” Recognize it as a shrub with foamy clusters of small flowers and signature leathery, oval, three-veined leaves. The flowers have a odor that fills the air when many are blooming, vaguely reminiscent of the smell of tobacco—whence its common name. The plant grows in most of our western mountain states to subalpine elevations. The closely related Ceanothus sanguineus Pursh (redstem ceanothus, or Oregon teatree, not shown) is important in forest reclamation, for the plants spring up on burned ground where its seeds have remained dormant for years, until activated by the heat of a wildfire.
	Cascara, Frangula purshiana (DC.) Cooper (left, right) is a small tree with strongly ribbed deep green leaves, small white flowers and sparse blue fruit (berries). It is attractive, and that may be why Meriwether Lewis gathered it near today’s Kamiah, Idaho, on May 29, 1806. Lewis made no mention of the bark’s purgative value—apparently the Nez Perce were unaware of this. Native Americans in California knew about cascara, however, and told Spanish priests about its laxative effect—explaining why the bark is known medically as cascara sagrada (Spanish for “sacred bark”). The trees were scarce for a while in Idaho because many were harvested for the bark. They are now grown commercially, and once again are found in fair numbers along the Clearwater River. Frederick Pursh named the plant but the name he gave it was already in use. When reclassified, his name was used to honor his role in classifying Lewis and Clark plants. Until recently, cascara was classified as a species of Rhamnus and is so listed in many guide books. The name Frangula was derived from the Latin frangere meaning “to break” for the brittle twigs of some species.

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