Bidens pilosa L.

Erect annual or short-lived perennial, 10–100 cm tall. Stems glabrous or sparsely hairy, ribbed, much-branched. Lvs glabrous to moderately hairy especially below, ciliate, petiolate, usually 3-foliolate with terminal leaflet larger, sometimes simple and not lobed to 3-lobed; leaflets sessile or shortly petiolulate, ovate to lanceolate, evenly serrate, acute to acuminate, (1)–2–10–(25) cm long. Upper cauline lvs becoming smaller, shortly petiolate, and more often simple and not lobed or 3-lobed. Capitula c. 6–10 mm diam. Outer involucral bracts 7–9, foliaceous, ciliate, linear to narrowly oblong-obovate, 3–6 mm long; inner bracts many, membranous, triangular to subulate, 4–6 mm long, with dark lined centre and pale margins. Receptacular scales similar to inner bracts but narrower. Florets usually all ☿, tubular, yellow-orange, sometimes c. 5 white ray florets present. Achenes flattened or 3–(4)-angled, ± linear, ribbed, dark brown, usually glabrous except for ribs ciliate near apex, sometimes with scattered hairs elsewhere, 5–9 mm long; awns mostly 3, sometimes 2, rarely 4, sometimes unequal, (0.5)–1.5–2.5 mm long.

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

Flowering: Aug.–May–(Jul.)