22.
Bidens tripartita
Linnaeus, Sp. Pl. 2: 831. 1753.
Bident à trois divisions
Bidens comosa
(A. Gray) Wiegand
Annuals,
(5—)20—70(—200) cm.
Leaves
sessile or petioles 5—15(—35+) mm (± winged); blades ± elliptic to ovate or lanceolate, 40—80(—150+) × 15—40(—60+) mm, sometimes laciniately 1-pinnatisect with 1—4+ lobes near bases, bases cuneate, margins entire or dentate to serrate, usually ciliate, apices acute to acuminate, faces glabrous or hirtellous.
Heads
borne singly or in 2s or 3s.
Peduncles
10—40(—80) mm.
Calyculi
of (2—)6—7(—10) ± spreading, oblanceolate or lanceolate to linear, ± foliaceous bractlets or bracts 7—35(—60) mm, margins (entire or serrate) sometimes sparsely ciliate, abaxial faces hispidulous near bases, distally glabrous.
Involucres
campanulate to hemispheric or broader, (4—)5—7(—12) × (3—)6—12(—15+) mm.
Phyllaries
(6—)7—8(—13), elliptic-ovate to lance-ovate, (4—)6—9(—12) mm.
Ray florets
usually 0, sometimes 1—5; laminae orange yellowish, 4—8 mm.
Disc florets
(5—)20—60(—150+); corollas pale yellow to orange, (2—)3—4 mm (gradually ampliate, anthers usually pale).
Cypselae
blackish to purplish or brown, ± flattened, sometimes weakly 3(—4)-angled, usually cuneate to linear, outer (3—)6—7(—10) mm, inner (4—)6—9(—11) mm, margins proximally antrorsely to patently, distally retrorsely, barbed, apices ± truncate to concave, faces ± 1-nerved, usually smooth, seldom notably tuberculate, glabrous or sparsely strigillose;
pappi
0, or of (1—)3—3(—4+) ± erect to spreading, retrorsely barbed awns (0.2—)2—3(—6) mm.
2
n
= 48.
Flowering Aug—Oct. Marshes and other wet sites; 10—1700 m; Alta., B.C., Man., Que.; Ala., Alaska, Calif., Colo., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., 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.; Europe; Asia; n Africa; introduced in Pacific Islands, Australia.
Plants with cypsela mid-nerves strongly developed (cypselae more or less strongly 4-angled and, often, tuberculate) that are treated below as
Bidens connata
have been included in
B. tripartita
, perhaps rightly so. And some botanists have included (or advocated inclusion of)
B. eatonii, B. heterodoxa
, and/or
B. infirma
in
B. tripartita
, as well, perhaps rightly so.
