Bidens frondosa seeds mature in Oc.大狼杷草 da lang pa cao. Annuals, 20-120 cm tall. Leaves petiolate; petiole 10-40(-60) mm; blade deltate to ovate-lanceolate overall, 30-80(-150) × 20-60(-100) mm, 3(-5)-foliolate, leaflets petiolulate, lanceolate to ovate-lanceolate, (15-)35-60(-120) × (5-)10-20(-30) mm, both surfaces glabrous or hirtellous, bases cuneate, margins dentate to serrate, sometimes ciliate, apices acuminate to attenuate. Capitula radiate or discoid, usually solitary, sometimes in 2s or 3s or in lax corymbs; peduncles 10-40(-80) mm; calycular bracts (5-)8(-10), ascending to spreading, spatulate or oblanceolate to linear, sometimes ± leaflike, 5-20(-60) mm, abaxially glabrous or hirtellous, margins usually ciliate; involucres campanulate to hemispheric or broader, 6-9 × 7-12 mm; phyllaries 6-12, oblong or ovate to ovate-lanceolate, 5-9 mm. Ray florets 0 or 1-3+; lamina golden yellow, 2-3.5 mm. Disk florets 20-60(-120+); corollas ± orange, 2.5-3+ mm. Achenes blackish to brown or straw-colored, ± obcompressed, obovate to cuneate, outer 5-7 mm, inner 7-10 mm, faces usually 1-veined, sometimes tuberculate, glabrous or sparsely hirtellous, margin antrorsely or retrorsely barbed, apices ± truncate to concave; pappus of 2 ± erect to spreading, antrorsely or retrorsely barbed awns 2-5 mm. Fl. Aug-Sep. 2n = 24, 48, 72.