Most regional floras consider the five subspecies to be separate species.
Leaves Branches erect to sprawling, covered with prickles. Flowers single or in clusters of two to three. Roots shallow, radiating from a central crown. Across boreal Canada from Hudson Bay to Alaska, south into the US to the Palouse, northern Rockies, Black Hills, Upper Missouri, and Great Lakes States. Rocky and sandy shores, stony banks, talus slopes and outcrops and in clearings, moist woods, and thickets, generally at low elevations in the boreal forest.