Plants perennial. Stems 5-8 dm, diffusely branched, often decumbent, copiously long-prickly. Leaf blades: surfaces sparingly long-prickly on veins; basal and proximal lobed nearly to midrib, lobe length often to 5 times width; distal not clasping. Inflorescences: buds ellipsoid-oblong, body 15-18 × 12-15 mm, prickly; sepal horns slender, terete, 12-15 mm, prickly at base. Flowers 7-10 cm broad; petals white; stamens 100 or more; filaments pale yellow; pistil 3-carpellate. Capsules narrowly ellipsoid-oblong, 35-45 × 10-14 mm (including stigma and excluding prickles), closely prickly, longest prickles 8-10 mm. Seeds ca. 2 mm.

Flowering spring; fruiting summer. Precipitous slopes; of conservation concern; 1000-2000 m; Ariz.

Argemone arizonica grows well in Grand Canyon National Park, especially along the Kaibab and Bright Angel trails.

Plant: herb or shrub; STEMS diffusely branched, often decumbent, very prickly, about 60-80 perpendicular prickles per square cm of surface, the largest prickles 7-10 mm long Leaves: prickly on the veins beneath, remotely prickly on the midrib above, glabrous between the veins; lower and middle cauline leaves lobed five-sixths to nine-tenths to the midrib, the lobes often five or more times as long as wide, the margin angular at the apex, the sinuses to five times the width of the main lobes; uppermost leaves similar but smaller INFLORESCENCE: cymose Flowers: buds elliptic-oblong; calyx with 80-120 perpendicular prickles per sepal, the sepal horn 12-15 mm long with 7-15 prickles near its base, the apical prickle terete at its base; petals white; stamens 150 or more Fruit: capsules fusiform, with 40-60 simple prickles per square cm of surface, the largest prickles 8-10 mm long; SEEDS numerous pitted Misc: Dry, precipitous slopes; 900-1500 m (3000-5000 ft); June REFERENCES: Ownbey, Gerald B., Jeffrey W. Brasher, and Curtis Clark. 1998 Papaveraceae. J. Ariz. - Nev. Acad. Sci. 30(2): 120.