Flora of New Zealand Series

N. Auckland - Glen Eden, Te Aroha, near Rotorua. Discard from cultivation in ponds.

(S. America; Venezuela, Brazil)

First record: Cheeseman 1914: 9.

First collection: Te Aroha, B. Neve, undated [c. 1914] (); Cheeseman (loc. cit.) cites Neve as collector.

FL. 2-3.

"Stoloniferous" perennial, tufts bright green. Stems semi-transparent, with internal septa. Leaves in tufts, floating on surface or projecting above surface, laminae to 7 × 6 cm, ovate, or orbicular-cordate, thick, shining, midrib swollen towards base on underside, 3 less prominent lateral nerves on either side all converging at leaf-tip; petiole very long, ± transparent, with internal septa. Flower solitary, yellow, conspicuous, slightly above water level; peduncle terete with basal membranous bract; sepals 1.5-2 cm long, narrow-ovate, green, shining, spongy, margins incurved, tip obtuse; petals c. 5 × 4 cm, broadly obovate, clear yellow, deeper yellow towards base, very fragile and ephemeral, ± lobed at tip. Stamens numerous, conspicuous, c. 1 cm long, in whorls from a spongy disc round carpels, inner stamens with sulphur-yellow anthers c. 5 mm long, outer sterile with reddish-purple filaments only. Follicles not seen.

Non-flowering plants apparently spread by "stolons", modified peduncles which produce at nodes a number of close-packed scale leaves and root readily there to form new plants.

H. nymphoides, with its broad, long-petiolate leaves, is likely to be confused only with Aponogeton distachyus and Ottelia ovalifolia, but it differs from these in the "stoloniferous" habit, absence of a distinct juvenile leaf form, ± cordate leaf blades, and large, solitary, yellow, poppy-like flowers.

Though apparently sterile in N.Z., this floating-leaved aquatic has appeared and spread aggressively in new localities in recent years. When thoroughly established in a creek at Glen Eden, Auckland, it formed a dense mat of "elastic stems", and in a bay of Lake Rotoehu, explosive growth over a 5 months period resulted (December 1976) in two large colonies-100 and 125 sq. metres in extent-which had developed from small initial plantings.

As the plant has been commercially propagated and sold recently in the northern half of N. Id it is likely that new occurrences arising from deliberate plantings will be detected in the future.

Fig. 1. Hydrocleys nymphoides, water poppy; A habit, showing ± cordate leaf blades, of one form only, B diagram of "stoloniferous" habit. © All rights reserved. [Image: 26WU]