Sp. Pl. 2: 675. 1753.
Herbs, annual or perennial, or subshrubs, to 2 m, taprooted. Leaves: petiole 0.3–5.5 cm; blade ovate to lanceolate, 1.3–9 × 1–7 cm, glabrate, hairs simple on veins. Inflorescences terminal, cymose glomerules, 10–25-flowered; bracteoles 3 or 4, immediately subtending flower. Flowers monomorphic; calyx 2–2.5 mm, teeth acute, distant and sinuses between them rounded; petals purple, pink, or white with yellow base, 3–6 × 1–1.5 mm; stamens and pistil equal, 2.5–3.2 mm. Fruits schizocarps, white, pink, green, purplish, or black, subglobose, not winged, not beaked, 4–5 × 5–6 mm, dehiscence loculicidal and then septicidal, fruit falling apart. Seeds 1 per locule. 2n = 36, 46.
Phenology: Flowering and fruiting (spring–)summer–fall.
Habitat: Agricultural lands, open pinelands, meadows, waste ground, wet or dry soil
Elevation: 0–300(–1000) m
Introduced; Ala., Ark., Fla., Ga., La., Miss., N.C., S.C., Tex., Asia, Pacific Islands (East Indies, Papua New Guinea, Philippines), Australia (Queensland), introduced also in Central America (Panama), South America (Brazil), Africa.