Feddes Repert. Spec. Nov. Regni Veg. 6: 161. 1908.
Plants annual or perennial. Stems branched, 5-12 dm, sparingly to closely prickly. Leaf blades: abaxial surface sparingly prickly on veins, adaxial surface unarmed or sparingly prickly on veins, apices of lobes angular, marginal teeth prominent; proximal lobed ca. 3/4 distance to midrib; distal sometimes clasping. Inflorescences: buds oblong-obovoid or subglobose, body 14-20 × 11-18 mm, prickly, prickles simple or branched; sepal horns terete or adaxially flattened, 4-12 mm. Flowers 8-12(-16) cm broad; petals white; stamens ca. 150; filaments pale yellow to red; pistil 3-4-carpellate. Capsules ovoid to ellipsoid-lanceoloid, 25-45 × 10-16 mm (including stigma and excluding prickles), closely to sparingly prickly, longest prickles 4-6(-8) mm. Seeds 2-2.5 mm.
Ariz., N.Mex., Western North America (United States and Mexico).
Subspecies 3 (3 in the flora).
|1||Capsules closely prickly; bud prickles often branched.||Argemone pleiacantha subsp. pleiacantha|
|1||Capsules sparingly prickly; bud prickles simple.||> 2|
|2||Blades of proximal leaves lobed 4/5 distance to midrib, distal not clasping.||Argemone pleiacantha subsp. pinnatisecta|
|2||Blades of proximal leaves lobed 1/2–2/3 distance to midrib, distal often clasping.||Argemone pleiacantha subsp. ambigua|