Bidens frondosa L.

Bidens frondosa plant

Family - Asteraceae

Stems - From fibrous roots, stout, erect, herbaceous, to +/-2m tall, branching, 4-angled (the angles rounded), fluted, essentially glabrous but with a few antrorse hairs in upper portions, typically purple.

Bidens frondosa stem

Leaves - Opposite, petiolate, trifoliolate. Petiole to +/-5cm long, with an adaxial groove (groove curly pubescent within), the rest of the petiole glabrous or with very sparse short pubescence. Lateral leaflets with petiolules to 5-6mm long, basally oblique. Terminal leaflet with petiolule to 2.5cm long, larger than lateral leaflets, sometimes unequally divided. All leaflets serrate, acuminate, puberulent above, pubescent below, to +10cm long, 4cm broad, light green below, deep dull green above.

Bidens frondosa leaves

Inflorescence - Loose cymose arrangement of flower heads.

Involucre - Outer series of bracts spreading, 5-8 in number, oblong-lanceolate to oblong-oblanceolate or spatulate, ciliate-margined, occasionally with a few coarse serrate teeth, to 3cm long, +/-6mm broad, antrorse pubescent below and above on midrib. Inner series to 1cm long, 8mm in diameter in flower. Inner bracts yellowish-green, subulate, erect, appressed, glabrous, to 7mm long, 3mm broad.

Bidens frondosa involucreInvolucre.

Ray flowers - Absent.

Disk flowers - Corolla 3.1mm long, whitish at base, yellowish in apical 1/2, glabrous, contracted in basal 1/2, 5-lobed. Lobes acute, yellow, spreading to erect, .4mm long, papillate internally. Stamens 5, adnate at apex of contracted portion of corolla tube. Filaments glabrous, whitish, 1.3mm long. Anthers connate around style, only partially exserted, 1mm long, purplish. Style exserted, bifurcate, yellowish at apex (stigmas). Achenes antrorsely barbed, compressed, to 5mm long. Awns 2, to +3mm long, retrorsely barbed. Chaff thin, transparent, yellowish-brown at apex, to 8-9mm long, 1.1mm broad, slightly folded, glabrous.

Bidens frondosa flower

Flowering - August - October.

Habitat - Wet ground, ditches, pond margins, streambanks, waste ground, roadsides, railroads.

Origin - Native to U.S.

Other info. - This species of Bidens can be found throughout Missouri. The plant described above is B. frondosa var. frondosa f. frondosa which has the retrorse barbs on its awns. Form anomala (Porter) Fern. has barbs which are antrorse on the awns. This latter form has not been found in Missouri.
Because this species grows close to water, it is eaten by muskrats. The achenes are eaten by ducks.

Photographs taken at The Summit Conference Center, Brown Summit, NC., 9-14-01, and along the shores of the Current River, Shannon County, MO., 9-20-03.