Herbs, perennial, 1-5 dm. Stems prostrate to procumbent, villous, glabrate. Leaves sessile; blade rhombic-ovate, oval, or obovate, usually longer than broad, 0.5-2.5 × 0.3-1.5 cm, apex rounded, apiculate, sparsely villous, glabrate. Inflorescences axillary, sessile; heads white to stramineous, ovoid, 0.5-0.8 × 0.4-0.6 cm; bracts shorter than tepals, apex long-attenuate, aristate. Flowers: tepals dimorphic, whitish to stramineous, lanceolate, 3-5 mm, apex acuminate, spinose tipped, densely villous, hairs barbed; stamens 5; pseudostaminodes triangular or subulate, shorter than filaments, margins usually entire, rarely dentate. Utricles included within tepals, brown, ovoid-orbicular, 1.5 mm, apex slightly truncate. Seeds ovate-orbiculate, 1-1.5 mm. Flowering summer-fall. Gravel, sand bars, sidewalks; 0-2000 m; introduced; Ala., Ariz., Ark., Calif., Fla., Ga., La., Md., Miss., N.Mex., N.C., Okla., S.C., Tex.; Mexico; Central America; South America.

Plant: perennial; stem wavy-hairy, becoming glabrous Leaves: at a node often unequal; simple, opposite; petioles 3-13 mm, narrowly winged, clasping; blades 5-18 mm wide, ± diamond-shaped to round, tip obtuse to acute INFLORESCENCE: spike, 6-7 mm wide, sessile; bracts 3-3.5 mm, entire, whitish, papery, midvein hairy Flowers: bisexual; sepals unequal, 5, outer 3.5-4.5 mm, ± widely lanceolate, not keeled, strongly 3-veined below, spine-tipped, inner 2.5 mm, ± linear, keeled, generally 1-veined, whitish, stiff, margins scarious; filaments 0.2-0.4 mm, slightly > staminodia; ovule pendent, style 1, short, stigma 0 or 2-lobed Fruit: indehiscent capsule; wall membranous; Seed smooth, hard Misc: waste places; < 150 m.