Bidens bipinnata
Sp. Pl. 2: 832. 1753.
Annuals, (15–)30–100(–150+) cm. Leaves: petioles 20–50 mm; blades rounded-deltate to ovate or lanceolate overall, (20–)30–70+ × (20–)30–60+ mm, (1–)2(–3)-pinnatisect, ultimate lobes obovate or lanceolate, 15–45+ × 10–25+ mm, bases truncate to cuneate, ultimate margins entire, sometimes ciliolate, apices rounded to acute or attenuate, faces usually glabrous, sometimes hirtellous. Heads usually borne singly, sometimes in ± corymbiform arrays. Peduncles (10–)20–50(–100) mm. Calyculi of (7–)8(–10) linear bractlets 3–5 mm, ± appressed, margins ciliate, abaxial faces usually glabrous. Involucres ± campanulate, 5–7 × 3–4(–5) mm. Phyllaries 8–12, lanceolate to linear, 4–6 mm. Ray florets 0 or 3–5+; laminae yellowish or whitish, 1–2(–3) mm. Disc florets 10–20(–30+); corollas yellowish to whitish, 2–3 mm. Cypselae red-brown, outer weakly obcompressed, 7–15 mm, inner ± 4-angled, linear to linear-fusiform, 12–18 mm, margins not ciliate, apices ± attenuate, faces 2-grooved, often tuberculate-hispidulous; pappi of (2–)3–4, erect to divergent, retrorsely barbed awns 2–4 mm. 2n = 24, 72.
Phenology: Flowering (Jun–)Aug–Sep(–Oct).
Habitat: Fields, forests, disturbed, wettish sites
Elevation: 10–1800 m
Distribution
N.B., Ont., Ala., Ariz., Ark., Conn., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Miss., Mo., Nebr., N.J., N.Mex., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va., South America, Europe, Asia, Pacific Islands.
Discussion
Bidens bipinnata is probably native in eastern Asia and introduced in South America, Europe, Asia, and Pacific Islands.
Selected References
None.