柳叶鬼针草 liu ye gui zhen cao

Bidens cernua var. elliptica Wiegand; B. cernua var. integra Wiegand; B. cernua var. minima (Hudson) Pursh; B. cernua var. oligodonta Fernald & H. St. John; B. cernua var. radiata Candolle; B. filamentosa Rydberg; B. glaucescens Greene; B. gracilenta Greene; B. minima Hudson; B. prionophylla Greene.

Annuals, 10-100 cm tall. Leaves sessile; blade ovate-lanceolate or oblanceolate to lanceolate or linear, 40-100(-200) × (2-)5-25(-45) mm, both surfaces glabrous, base cuneate to rounded, margin usually coarsely dentate to serrate, sometimes entire, sometimes ciliate, apex acute to acuminate. Capitula radiate, rarely discoid, solitary or in lax corymbs; peduncles 10-40(-100+) mm; calycular bracts (3-)5-8(-10), spreading to reflexed, oblong to linear-lanceolate, often ± leaflike, (3-)8-12(-25) mm, abaxially usually glabrous, bases sometimes hispidulous, margin usually ciliate; involucres hemispheric or broader, (3-)6-10 × (8-)12-20+ mm; phyllaries 6-8+, ovate or ovate-lanceolate to lanceolate, 2-10 mm. Ray florets usually 6-8, sometimes absent; lamina orange-yellow, 2-15(-18) mm. Disk florets (10-)40-100(-150+); corollas orange-yellow, 3-4 mm. Achenes blackish or brown, usually flattened, sometimes 4-angled, cuneate, outer (3-)5-6 mm, inner 4-8 mm, faces ± striate, glabrous or tuberculate-strigillose, margin thickened or winged, retrorsely ciliate, apices truncate to convex; pappus of (2-)4 retrorsely barbed awns (1-)2-4 mm. Fl. Aug-Oct. 2n = 24, 48.

Swamps, marshes, peat and sedge bogs, flood plains; sea level to 2300 m. Hebei, Heilongjiang, Jilin, Liaoning, Nei Mongol, Sichuan, Xizang, Yunnan [Mongolia, Russia; Europe, North America].