Distribution: Occurring east of the Cascades crest, where endemic along the Snake River in Whitman County, Washington;
Habitat: Moist hillsides, usually along streams.
Flowers: May - June
Conservation Status: Threatened in Washington (WANHP)
Strong, deciduous perennial, the primocanes erect to clambering, glabrous, greenish and glaucous, up to 5 m. long, the prickles straight and flattened; flowering stems trailing, up to 5 m. long, armed with flattened, hooked prickles.
Leaves green and glabrous on both surfaces, trifoliate on the flowering stems but 5- foliate on the canes, the lower 2 leaflets sessile; leaflets ovate-lanceolate, doubly lobed-serrate.
Flowers 1-5 in small, loose clusters; sepals 5, spreading, 5-8 mm. long; petals white, elliptic, 4-7 mm. long, often more than 5; stamens 75-100, pistils 25-40.
Drupelets barely coalescent, blackish, strongly roughened, rather dry, free from the receptacle.