Bidens biternata - (Lour.) Merr. & Sherff.
Yellow-flowered black jack
Bidens cylindrica Sherff.
Color Of Flower
Achenes not beaked
Annual or perennial, erect, glabrous, pilose or sparsely pubescent herb; branches angular, straight; leaves opposite, simple or pinnately 3-7 lobed, lateral leaflets ovate, dentate or serrate, acute at apex, terminal leaflet elliptic, sparsely dentate; petiole slightly winged at the base; heads on dichotomously branched long, stout peduncles; involucral bracts 2-seriate, connate, outer bracts short, linear-lanceolate, ciliate at margins, inner bracts broad, ovate-lanceolate, glabrous; ray florets usually-3, whitish or creamy yellow, often 3-lobed; disk florets many, dark purple, 5-lobed; achenes long, black, much exceeding the involucres, very slender, tetragonous or compressed, 2-4 stout awns, covered with recurved hooks; pappus bristles 3-4 with reflexed hairs.