Crowned Beggarticks

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.

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.

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

Bidens trichosperma, the marsh beggar-ticks or marsh tickseed, is a North American species of flowering plant in the family Asteraceae. It is native to central Canada (Quebec, Ontario) and to the eastern and north-central United States (primarily the Northeast, Great Lakes, and northern Great Plains, with a few isolated populations in the Southeast).

Bidens trichosperma is an annual herb up to 150 cm (60 inches) tall. It produces numerous yellow flower heads containing both disc florets and ray florets. The species is commonly found in marshes and along estuaries.

It should not be confused with Bidens coronata, which it was once considered synonymous with. Both species may be referred to as crowned beggar-ticks but the name properly belongs to coronata.