Bidens frondosa L.

Erect, glabrous or almost glabrous annual, 20–200 cm tall. Stems angled, branched above to form infl., and sometimes from base. Lvs petiolate, 1-pinnate, with 1–2 pairs of leaflets and a slightly larger terminal leaflet; leaflets sessile or shortly petiolulate, narrow-ovate to lanceolate, coarsely or unevenly serrate, acuminate, (1)–2–13 cm long. Upper cauline lvs becoming smaller, shortly petiolate, and often simple and not lobed or 3-lobed. Capitula 10–20 mm diam. Outer involucral bracts 4–9, foliaceous, usually ciliate at least at base, sometimes glabrous, linear to narrowly oblong-obovate, (10)–15–30 mm long; inner bracts many, membranous, triangular to subulate, 6–10 mm long, with dark lined centre and pale margins. Receptacular scales similar to inner bracts but narrower. Florets usually all ☿, tubular, yellow-orange, rarely a few orange ray florets present. Achenes flattened, ovate-cuneate with 1 slender rib on each face, dark brown, ciliate, and otherwise glabrous to sparsely hairy, 6–10 mm long; awns 2, 2.5–4.5 mm long.

[From: Webb et al. (1988) Flora of New Zealand. Volume 4.]

Flowering: Nov.–May.