in A. von Humboldt et al., Nov. Gen. Sp. 2: 206. 1818.
Herbs, perennial, 3–8 dm. Stems prostrate, villous. Leaves sessile; blade oval to obovate, usually as broad as long, 1.3–3 × 1.1–1.7 cm, apex rounded, pilose, glabrate. Inflorescences axillary, sessile; heads stramineous, globose to ovoid, 0.6–1 × 0.6–0.7 cm; bracts equaling tepals, apex attenuate. Flowers: tepals dimorphic, stramineous, lanceolate, 5–7 mm, apex acuminate, spinose tipped, sparsely villous, hairs barbed; stamens 5; anthers 3–5, globose; pseudostaminodes triangular, shorter than filaments, margins dentate. Utricles included within tepals, brown, compressed, 1.8 mm, apex truncate. Seeds lenticular, 1.3–1.5 mm.
Phenology: Flowering summer–fall.
Habitat: Waste grounds, cleared limestone areas
Elevation: 0-1500 m
Introduced; Ala., Fla., La., N.Y., Tex., West Indies, South America.
Alternanthera pungens was long known as A. repens (Linnaeus) Link, a later homonym of A. repens J. F. Gmelin.