Bidens aurea

Annuals [perennials], (10–)50–100[–250] cm. Leaves: petioles 20–40 mm; blades deltate or lanceolate to lance-linear overall, (30–)50–120(–220) × 10–50(–150) mm, sometimes either 1-pinnately lobed, primary lobes 3–5+, lanceolate to lance-linear, 30–120 × 3–25+ mm, or 2-pinnatisect, ultimate lobes linear, 5–30 × 1–2+ mm, bases truncate to cuneate, ultimate margins entire or serrate, seldom ciliate, apices obtuse to acuminate, faces glabrous or puberulent. Heads in ± corymbiform arrays. Peduncles (10–)40–60+ mm. Calyculi of 8–12(–17) usually erect, linear, seldom foliaceous bractlets 3–6 mm, margins ciliate, abaxial faces usually glabrous, sometimes hispidulous at bases. Involucres campanulate to hemispheric, 4–6 × 5–10 mm. Phyllaries 8–12, ovate to lanceolate, 4–5(–7) mm (margins usually yellow). Ray florets 5–6; laminae yellow, 10–30 mm. Disc florets 12–30(–60+); corollas yellowish, 3–4 mm. Cypselae dark brown to blackish, ± flattened, sometimes unequally 3–4-angled, ± linear, outer 4–6 mm, inner 5–7 mm, margins not barbed or ciliate, apices truncate, faces weakly 2-grooved, glabrous or sparsely strigillose, sometimes tuberculate; pappi 0, or of (1–)2(–4) erect to spreading, retrorsely barbed awns (1–)1.5–4 mm. 2n = 24 (Mexico).

Phenology: Flowering mostly Aug–Sep.
Habitat: Marshes, borders of streams, other wet sites
Elevation: 900–2000 m

Ariz., Mexico, Central America, introduced in Europe.

Discussion

Selected References

None.

Lower Taxa