Hort. Bot. Hafn. 2: 489. 1815.
Plants annual or biennial. Stems 4-10(-15) dm, sparingly to moderately prickly. Leaf blades: abaxial surface sparingly prickly on main veins, adaxial surface unarmed or sparingly prickly on main veins; basal and proximal lobed 1/2-4/5 distance to midrib; distal clasping. Inflorescences: buds broadly ellipsoid to subglobose, body 12-18 × 10-16 mm, sparingly to rather closely prickly; sepal horns terete, 3-6(-10) mm, usually unarmed. Flowers 5-10 cm broad, closely to more distantly subtended by 1-2 foliaceous bracts; petals white; stamens 150 or more; filaments lemon yellow; pistil (3-)4-5(-7)-carpellate. Capsules oblong, oblong-ellipsoid, or narrowly ellipsoid, 20-40(-45) × 10-15(-25) mm (including stigma and excluding prickles), prickly, surface clearly visible to partially obscured, longest prickles widely spaced, 6-10(-12) mm, sometimes interspersed with smaller ones. Seeds 1.6-2 mm.
Ala., Ark., Conn., Fla., Ga., Ill., La., Mass., Mich., Miss., Mo., N.C., N.Y., S.C., Tex.
Subspecies 2 (2 in the flora).
|1||Capsules oblong to oblong-ellipsoid, prickles equal, widely spaced.||Argemone albiflora subsp. albiflora|
|1||Capsules usually narrowly ellipsoid, prickles unequal, longer ones widely spaced, interspersed with shorter, unequal ones.||Argemone albiflora subsp. texana|