狼杷草 lang pa cao

Bidens repens D. Don; B. shimadae Hayata; B. tripartita var. quinqueloba C. H. An; B. tripartita var. repens (D. Don) Sherff; B. tripartita var. shimadae (Hayata) Yamamoto.

Annuals, 10-150 cm tall. Leaves sessile or petiolate; petiole (0-)5-15(-35) mm (± winged); blade elliptic to ovate or lanceolate, 40-80(-150) × 15-40(-60) mm, sometimes laciniately 1-pinnatisect with 1-4+ lobes near base, both surfaces glabrous or hirtellous, base cuneate, margin entire or dentate to serrate, usually ciliate, apex acute to acuminate. Capitula radiate or discoid, solitary or in 2s or 3s; peduncles 10-40(-80) mm; calycular bracts (2-)6 or 7(-10), spreading, oblanceolate or lanceolate to linear, ± leaflike, 7-35(-60) mm, abaxially hispidulous near bases, distally glabrous, margins entire or serrate, sometimes sparsely ciliate; involucres campanulate to hemispheric or broader, (4-)5-7(-12) × (3-)6-12(-15) mm; phyllaries (6 or)7 or 8(-13), elliptic-ovate to ovate-lanceolate, (4-)6-9(-12) mm. Ray florets usually 0, sometimes 1-5; lamina orange yellowish, 4-8 mm. Disk florets (5-)20-60(-150); corollas pale yellow to orange, (2-)3-4 mm, apex 4- or 5-toothed. Achenes blackish to purplish or brown, ± flattened, sometimes weakly 3(or 4)-angled, usually cuneate to linear, outer (3-)6-7(-10) mm, inner (4-)6-9(-11) mm, faces ± 1-veined, usually smooth, seldom notably tuberculate, glabrous or sparsely strigillose, margin proximally antrorsely to patently, distally retrorsely, barbed, apices ± truncate to concave; pappus 0, or of 1-3(or 4) erect to spreading, retrorsely barbed awns (0.2-)2-3(-6) mm. Fl. Jul-Oct. 2n = 48.

Marshes and other wet sites, waste fields, roadsides. Anhui, Fujian, Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Bhutan, India, Indonesia, Japan, Korea, Malaysia, Mongolia, Nepal, Philippines, Russia; N Africa, Australia, Europe, North America].

This is a worldwide weed.