Plants annual or biennial. Stems 4-8(-12) dm, sparingly prickly. Leaf blades: abaxial surface scattered-prickly on main veins, adaxial surface unarmed; proximal lobed 2/3 distance to midrib; distal clasping. Inflorescences: buds ellipsoid-oblong, body 15-22 × 10-15 mm, sparingly prickly; sepal horns terete, 6-10(-15) mm, usually unarmed. Flowers 7-10 cm broad, usually closely subtended by 1-2 foliaceous bracts; petals white, very rarely lavender; stamens 150 or more; filaments lemon yellow; pistil 3-4-carpellate. Capsules narrowly to broadly ellipsoid, 35-50 × 10-17 mm (including stigma and excluding prickles), prickly, surface clearly visible, prickles widely spaced, longest 4-10(-12) mm, interspersed with a few shorter ones. Seeds ca. 2 mm. 2 n = 28.

Flowering spring-summer; fruiting late spring-summer. Prairies, foothills and mesas; 300-2300 m; Colo., Kans., Mont., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Utah, Wyo.

Argemone polyanthemos is introduced in Utah.

Ownbey et al. 1998

Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Plants annual or biennial, stems 40-80 cm tall, sparingly prickly. Leaves: Distal clasping, abaxial surface scattered-prickly on main veins, adaxial surface unarmed; proximal lobed 2/3 distance to midrib. Flowers: Buds ellipsoid-oblong, body 15-22 mm by 10-15 mm, sparingly prickly; sepal horns terete, 6-10 mm, usually unarmed; 7-10 cm broad, usually closely subtended by 1-2 foliaceous bracts; white petals, very rarely lavender, stamens 150 or more, filaments lemon yellow, pistil 3-4 carpellate. Fruits: Capsule narrowly to broadly ellipsoid 35-50 mm by 10-17 mm (including stigma and excluding prickles), prickly, surface clearly visible, prickles widely spaced, longest 4-10 mm, interspersed with a few shorter ones. Ecology: Found on prairies, foothills and mesas 1,000-7,500 ft (305-2286 m); flowers March-August. Notes: Huge questions about this species collection, as Flora of Arizona mentions neither A. polyanthemos or its predecessor A. intermedia as occurring here. Flora of North America does not list it as being in AZ, neither does Plants DB, could simply be a subspecies of A. pleicantha, likely subsp. ambigua. Ethnobotany: Unknown for this species, but many other uses for species in this genus.  Etymology: Argemone from Greek argemos, a white spot (cataract) on the eye, what it was supposed to cure, polyanthemos refers to having many anthers. Synonyms: Argemone platyceras Editor: SBuckley, 2010