Annuals, (5-)25-35(-55+) cm. Leaves: petioles (narrowly, if at all, winged) 5-20(-35+) mm; blades lanceolate to lance-linear, (20-)30-50(-80+) × (3-)6-20(-30+) mm, sometimes laciniately 1-pinnatisect with 2-4+ lobes near bases, bases cuneate, margins incised to serrate, seldom ciliate, apices acute to attenuate, faces glabrous. Heads borne singly or in 2s or 3s. Peduncles 10-35(-55) mm. Calyculi of (2-)3-5(-7) ± erect, oblanceolate or spatulate to linear, ± foliaceous bractlets or bracts (6-)10-25(-40+) mm, margins rarely ciliate, abaxial faces usually glabrous, sometimes sparsely hispidulous. Involucres usually obconic to broadly campanulate, rarely hemispheric, (4-)6-7 × (4-)5-7 mm. Phyllaries (4-)5-8, oblong to lance-ovate, (4-)5-8+ mm. Ray florets usually 0, sometimes 1-3+; laminae orange yellowish, 2-5(-10) mm. Disc florets (7-)20-70+; corollas yellowish, 2.5-3.5 mm. Cypselae: outer red-brown, ± flattened, sometimes 3-4-angled, broadly cuneate, 4-5(-6) mm, inner blackish, narrowly cuneate, (5-)6-7(-8+) mm, margins glabrous or sparsely antrorsely strigillose, apices ± truncate to convex, faces ± 1-nerved, glabrous or sparsely setulose, usually smooth, sometimes ± tuberculate; pappi 0, or of 2(-4) spreading to divergent, antrorsely or retrorsely barbed awns (0.1-)1-3.5+ mm. 2n = 48.

Flowering Aug-Oct. Borders of estuaries, lakes, marshes, streams; 0-10 m; N.B., P.E.I., Que.; Conn.

Bidens heterodoxa may be better treated as part of B. tripartita.

consists of a series of rare and local coastal and subcoastal populations from Conn. to Que., to some extent estuarine, approaching B. eatonii in achenes and pappus (variously antrorsely or retrorsely barbed or barbless) but with broader, more numerously fld heads as in B. connata. The proper taxonomic status of these plants is uncertain.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.