Flora of New Zealand Series

marsh yellow cress

Perennial rhizomatous herb. Stems erect, glabrous or finely hairy, 30-80 cm tall. Lvs ± glabrous, variable in shape, spathulate- oblanceolate, cuneate; margins toothed. Lower lvs petiolate, auriculate at base, deeply pinnatifid with lobes becoming shallower toward apex, 8-16 × 2-6-(7) cm. Upper lvs smaller, pinnatifid or toothed, sometimes linear; auricles becoming 0. Pedicels glabrous, erecto-patent to patent, sometimes deflexed at fruiting, (5)-7-10-(12) mm long. Sepals 2-3 × 1 mm. Petals bright yellow, 3-6 mm long. Silicle glabrous, elliptic to ovoid, 1.5-3-(4) × 0.6-1-(2) mm, but often not or poorly developed; valves veinless; style 1 mm long. Seeds reddish brown, c. 1 mm long, finely colliculate, in 2 rows per locule.

N.: Northland, Auckland, Waikato, Bay of Plenty.

Temperate Eurasia, N. Africa 1870

Waste land near rivers and streams, arable land, nearly always in damp or wet situations.

Because of its perennating rhizomatous habit, large colonies of R. amphibia may consist of a single genotype; as the sp. is also self-incompatible plants often do not set seed. It was first recorded in N.Z. as Nasturtium amphibium.