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.
Annual or biennial, 4-10(15) dm; lvs not blotched; fls usually closely subtended by the upper lvs; pet white or rarely suffused with pink, 2-4 cm; stamens 100 or more; 2n=28. Dry, open, often sandy places, especially in disturbed sites; se. U.S., occasionally escaped from cult. n. to Ill. and Conn. May-Aug. (A. alba and A. intermedia, misapplied)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.