Ageratina riparia (Regel) R.M.King & H.Rob.

Erect or sprawling perennial herb to subshrub, 0.3–1–(2) m tall. Stems moderately to densely clothed in purple-striped eglandular hairs at least above, often tinged purple, much-branched. Lvs opposite; petiole hairy, 12–20 mm long; lamina glabrescent to sparsely hairy especially on veins of lower surface, narrow-elliptic to lanceolate, acuminate, coarsely serrate except near base, (30)–60–100–(130) × (8)–15–25–(40) mm; uppermost lvs smaller, sometimes entire. Capitula 4–5 mm diam., many in terminal corymbs; peduncle clothed in eglandular hairs. Involucral bracts in 2 ± equal rows, usually with shorter, narrower supplementary bracts outside, narrow-elliptic to lanceolate, hairy, 4–5 mm long. Florets white. Achenes black, 5-angled, hairy especially on angles, 1.5–2 mm long.

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

Flowering: Aug.–Jan.–(Mar.)