Bidens trichosperma

(Michaux) Britton

Bull. Torrey Bot. Club 20: 281. 1893

Basionyms: Coreopsis trichosperma Michaux Fl. Bor.-Amer. 2: 139. 1803
Synonyms: Bidens coronata var. brachyodonta Fernald Bidens coronata var. tenuiloba (A. Gray) Sherff Bidens coronata var. trichosperma (Michaux) Fernald
Treatment appears in FNA Volume 21. Treatment on page 213. Mentioned on page 207.
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.

Phenology: Flowering Aug–Oct.
Habitat: Marshes, estuaries
Elevation: 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.



Lower Taxa

No lower taxa listed.