Annuals, (10-)20-60(-180) cm. Leaves: petioles 10-40(-60) mm; blades deltate to lance-ovate overall, 30-80(-150+) × 20-60(-100+) mm, 3(-5)-foliolate, leaflets petiolulate, lanceolate to lance-ovate, (15-)35-60(-120) × (5-)10-20(-30) mm, bases cuneate, margins dentate to serrate, sometimes ciliate, apices acuminate to attenuate, faces glabrous or hirtellous. Heads usually borne singly, sometimes in 2s or 3s or in open, corymbiform arrays. Peduncles 10-40(-80+) mm. Calyculi of (5-)8(-10) ascending to spreading, spatulate or oblanceolate to linear, sometimes ± foliaceous bractlets or bracts 5-20(-60) mm, margins usually ciliate, abaxial faces glabrous or hirtellous. Involucres campanulate to hemispheric or broader, 6-9 × 7-12 mm. Phyllaries 6-12, oblong or ovate to lance-ovate, 5-9 mm. Ray florets 0 or 1-3+; laminae golden yellow, 2-3.5 mm. Disc florets 20-60(-120+); corollas ± orange, 2.5-3+ mm. Cypselae blackish to brown or stramineous, ± obcompressed, obovate to cuneate, outer 5-7 mm, inner 7-10 mm, margins antrorsely or retrorsely barbed, apices ± truncate to concave, faces usually 1-nerved, sometimes tuberculate, glabrous or sparsely hirtellous; pappi of 2 ± erect to spreading, antrorsely or retrorsely barbed awns 2-5 mm. 2n = 24, 48, 72. Flowering (Jun-)Aug-Sep(-Oct). Moist woods, meadows, thickets, fields, roadsides, railroads, borders of streams, ponds, sloughs, swamps, ditches; 10-2000 m; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Sask.; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; introduced, Europe. Infusions and tinctures of Bidens frondosa are rated as outstanding herbal therapies for irritation, inflammation, pain, and bleeding of the urinary tract mucosa and are used for benign prostatic hypertrophy and increasing excretion of uric acid, decreasing the risk of gout attacks, as well as other medical uses (M. Moore 1993).
Annual, generally glabrous or nearly so, 2-12 dm; lvs on petioles 1-6 cm, pinnately compound, with 3-5 lanceolate, acuminate, serrate lfls to 10 נ3 cm, sometimes sparsely short-hairy beneath, at least the terminal one slender-petiolulate; heads campanulate to hemispheric, or narrower in depauperate plants, discoid or nearly so, the disk to 1 cm wide in fl; outer invol bracts 5-10, typically 8, green and ±leafy, usually conspicuously surpassing the orange disk, evidently ciliate on the margins, at least toward the base; anthers exserted; achenes flat, narrowly cuneate, strongly 1-nerved on each face, commonly dark brown or blackish, subglabrous or appressed-hairy, 5-10 mm; pappus of 2 retrorsely (seldom antrorsely) barbed awns; 2n=24, 36, 48, 72. Waste places, especially in wet soil; Nf. and N.S. to Wash., s. to Ga., La., and Calif. June-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.