Coreopsis trichosperma Michaux, Fl. Bor.-Amer. 2: 139. 1803; Bidens coronata (Linnaeus) Britton var. brachyodonta Fernald; B. coronata var. tenuiloba (A. Gray) Sherff; B. coronata var. trichosperma (Michaux) Fernald

Annuals (biennials), (15–)30–50(–150+) cm. Leaves: petioles 5–20+ mm; blades ± deltate to ovate overall, 40–75(–150) × 10–45(–130) mm, usually laciniately 1–2-pinnatisect, ultimate lobes (3–)5–7+, oblanceolate or lanceolate to linear, (5–)10–30(–80+) × (1–)4–8(–12+) mm, bases cuneate, ultimate margins incised, dentate, serrate, or entire, little, if at all, ciliate, apices acute to attenuate, faces glabrous or ± hirtellous to strigillose. Heads usually in open, ± corymbiform arrays. Peduncles 20–150 mm. Calyculi of (6–)8(–11), ascending to spreading, spatulate to linear, sometimes ± foliaceous bractlets or bracts 3–10(–18) mm, margins sometimes ciliate, abaxial faces glabrous. Involucres hemispheric or broader, 4–6(–8) × 6–12 mm. Phyllaries 6–8(–10), oblong, 3–8 mm. Ray florets (7–)8–9; laminae golden yellow, 10–30 mm. Disc florets 40–60(–80+); corollas yellow, 3–5 mm. Cypselae blackish or brown, flattened, narrowly cuneate, outer 3–6 mm, inner 5–9 mm (lengths mostly 2.5–4 times widths), margins antrorsely barbed or ciliate, apices ± truncate, faces obscurely 1-nerved, sometimes tuberculate, glabrous or sparsely hispidulous; pappi of 2 erect, ± patently barbed awns or scales (0.4–)1–2.5(–4) mm. 2n = 24.

Flowering Aug–Oct. Marshes, estuaries; 0–300 m; Ont., Que.; Ala., Ark., Conn., Del., Fla., Ga., Ill., Ind., Iowa, Ky., Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., S.Dak., Tenn., Va., W.Va., Wis.

Plants here called Bidens trichosperma have long been known as B. coronata (Linnaeus) Britton (or Britton ex Sherff). Alas, Britton’s B. coronata (1913) is a later homonym of B. coronata Fischer ex Colla (1834) and cannot be used.