Plants annual. Stems often branching from base, 2.5-8 dm, unarmed or sparingly prickly. Leaf blades: surfaces unarmed or sparingly prickly on veins; proximal lobed 1/2 or more distance to midrib; distal more shallowly lobed, mostly clasping. Inflorescences: buds subglobose, body 10-15 × 9-13 mm, unarmed or sparingly prickly; sepal horns terete, 5-10 mm, unarmed. Flowers 4-7 cm broad, subtended by 1-2 foliaceous bracts; petals bright yellow or rarely pale lemon yellow; stamens 30-50; filaments yellow; pistil 4-6-carpellate. Capsules oblong to broadly ellipsoid, 25-45 × 12-20 mm (including stigma and excluding prickles when present), unarmed or prickly, longest prickles 6-10 mm. Seeds 1.6-2 mm. 2 n = 28. Flowering and fruiting spring-fall, or throughout year in tropics. Waste places, often a weed of roadsides, dooryards, fallow fields; 0-1500 m; Ont.; Ala., Conn., Fla., Ga., Ill., Ind., Kans., La., Md., Mass, Mich., Mo., Nebr., N.J., N.Y., N.C., Pa., S.C., Tenn., Tex., Va.; Mexico; West Indies; Central America. Argemone mexicana is probably native to southern Florida as well as the Caribbean islands and has been introduced along the coast of the United States from New England to Texas and, more infrequently, inland. Although it has been reported from Mississippi, no specimens are known. It is widespread in temperate and tropical regions around the world by introduction.
FNA Vol. 3, Kearney and Peebles 1969
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Herbaceous perennials, to 80 cm tall, stems stout, erect, leafy, often branching from the base, unarmed or sparingly prickly. Leaves: Alternate, sessile, basal leaves in a basal rosette, proximal blades lobed at least half or more distance to the midribs, becoming more shallowly lobed and clasping proximally, margins dentate, each tooth terminated by a prickle, surfaces unarmed or sparingly prickly on veins, glaucous, often mottled over veins. Flowers: Bright to pale lemon yellow, large and showy, 4-7 cm broad, with large, delicate petals with rounded tips, subtended by 1-2 foliaceous bracts, buds subglobose, 10-15 mm long and 9-13 mm wide, unarmed or sparingly prickly, sepals 2-3, unarmed or prickly, each with an erect, subterminal, hollow horn tipped with a prickle, sepal horns terete, 5-10 mm, unarmed. stamens 30-50 with yellow filaments, pistils 4-6-carpellate, pistils 3-4-carpellate, ovaries 1-locular, styles short, to 3 mm long in fruit, stigmas 3-7-lobed, infloresences with subglobose buds 10-15 mm long and 9-13 mm wide, unarmed or sparingly prickly. Fruits: Oblong to broadly ellipsoid capsules, 25-45 mm long and 12-20 mm long (including stigmas and excluding prickles when present), unarmed or prickly, the longest prickles 6-10 mm long, fruits erect and dehiscing from apex, surfaces scattered-prickly and stil Ecology: Found in waste places, often a weed of roadsides, dooryards, fallow fields, around 5,000 ft (1524 m); flowering April-May. Distribution: This species grows mainly in the eastern portions of the United States, but is also found in Texas and Arizona. Notes: This species enjoys sandy washes and roadsides, and has bright to light yellow flowers and is not or lightly prickly throughout. Kearney and Peebles note this species is probably introduced from tropical America. Ethnobotany: Specific uses for this species are unknown, but other species in the genus have uses. Synonyms: Argemone leiocarpa Editor: LCrumbacher2012 Etymology: Argemone comes from the Greek argemos, "a white spot (cataract) on the eye," which this plant was once supposed to cure, and mexicana means of or from Mexico.
Annual, mostly 2.5-8 dm; lvs usually blotched with paler green; fls closely subtended by the upper lvs; pet yellow or cream, 1.5-3.5 cm; stamens 30-50; 2n=28. Native of tropical Amer., occasionally escaped from cult. as far n. as Mass. May-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.