Jacobaea aquatica (Hill) P.Gaertn., B.Mey. & Scherb.

Erect, biennial herb, 20–70 cm tall. Stems densely lanate when young but soon glabrous, branched or not from base. Basal lvs lanate when young, soon almost glabrous, petiolate; petiole < lamina, amplexicaul; lamina pinnatifid toward base or not lobed, ovate-oblong to elliptic, obtuse to subacute at apex, regularly or irregularly crenate or serrate, c. 25–120 × 15–50 mm; venation pinnate. Cauline lvs lyrate-pinnatifid to 1-pinnate with irregularly once-toothed, oblong segments; uppermost lvs apetiolate, pinnatisect with narrow segments. Capitula in open panicles. Supplementary bracts 3–10–(16), lanceolate, 1.5–6 mm long. Involucral bracts 13–22, ovate-oblong, usually glabrous, sometimes sparsely hairy, 3.5–5.5 mm long. Ray florets 13–20; ligules yellow, 5–11 mm long. Disc yellow. Achenes terete, usually glabrous, rarely innermost sparsely hairy, c. 2 mm long; pappus 3–3.5 mm long.

[From: Webb et al. (1985) Flora of New Zealand. Volume 4 as Senecio aquaticus Hill]