Mem. Amer. Acad. Arts 4: 5. 1849.
Plants perennial. Stems 3-6 dm, densely prickly and crisped-hispid. Leaf blades: surfaces sparsely to densely crisped-hispid between veins, abaxial surface mostly densely prickly on midrib and main veins, adaxial surface less so; proximal lobed 4/5 distance to midrib; distal not clasping. Inflorescences: buds oblong, body 16-20 × 14-18 mm, prickly and hispid; sepal horns 4-7 mm, prickly, apical prickle flattened, indurate. Flowers 7-10 cm broad; petals white; stamens 150 or more; filaments pale yellow; pistil 3-4-carpellate. Capsules ovoid, 30-40 × 12-18 mm (including stigma and excluding prickles), densely prickly, surface obscured, longest prickles straight or incurved, ca. 5 mm. Seeds ca. 2.5 mm.
Phenology: Flowering spring–summer; fruiting summer–fall.
Habitat: Prairies, slopes, and eastern foothills of the Laramie and Rocky mountains
Elevation: 1400-2100 m
Colo., N.Mex., Wyo.