Bidens pilosa Linnaeus var. bipinnata (Linnaeus) J. D. Hooker.

Annual herbs, (15-)30-100(-150+) cm. Petioles 20-50 mm; leaf blade orbicular-deltate to ovate or lanceolate overall, (20-)30-70+ × (20-)30-60+ mm, (1 or)2(or 3)-pinnatisect, ultimate lobes obovate or lanceolate, 15-45+ × 10-25+ mm, both surfaces usually glabrous, sometimes hirtellous, bases truncate to cuneate, ultimate margin entire, sometimes ciliolate, apices rounded to acute or attenuate. Synflorescences of solitary capitula or ± corymbose; peduncles (10-)20-50(-100) mm. Capitula radiate or discoid; calycular bracts (7 or)8(-10), linear, 3-5 mm, ± appressed, abaxially usually glabrous, margin ciliate; involucres ± campanulate, 5-7 × 3-4(-5) mm; phyllaries 8-12, lanceolate to linear, 4-6 mm. Ray florets absent or 3-5+; lamina yellowish or whitish, 1-2(-3) mm. Disk florets 10-20(-30+); corollas yellowish to whitish, 2-3 mm. Achenes red-brown, outer weakly obcompressed, 7-15 mm, inner ± 4-angled, linear to linear-fusiform, 12-18 mm, faces 2-grooved, often tuberculate-hispidulous, margin not ciliate, apex ± attenuate; pappus of (2 or)3 or 4 erect to divergent, retrorsely barbed awns 2-4 mm. Fl. Aug-Oct. 2n = 24, 72.

Fields, forests, disturbed wettish sites; below 1800(-3000) m. Anhui, Fujian, Gansu, Guangdong, Guangxi, Hebei, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [Cambodia, Korea, Laos, Nepal, Thailand, Vietnam; Europe, North and South America, Pacific islands].