Flora of New Zealand Series

Perennial herb forming small to large and extensive, loose to fairly dense mats; stems decumbent, rooting at nodes, ascending at tips, much-branched. Lvs connate at base, 2.3-7 × 0.7-1.6 mm, 0.5-0.8 mm thick, narrowly lanceolate, oblong-lanceolate or elliptic-lanceolate, flattened above, strongly convex below; apex rounded to ± acute. Fls solitary in lf axils, star-like, 4-merous, 3-3.5 mm diam.; pedicels 2-5-(7) mm long, not elongating at fruiting. Calyx lobes 1-1.5 × 0.5-0.6 mm, triangular-ovate, acute or subacute. Petals 1.2-1.8 × 0.8-1 mm, broadly elliptic-ovate, white with pink flush, subacute, somewhat > calyx. Scales c. 0.7 mm long, oblanceolate. Follicles smooth. Seed c. 0.5 mm long.

S.: coastal areas from N.W. Nelson to Fiordland.

Also indigenous to temperate Australia.

Lake margins, river margins and around river mouths, salt marshes.

FL Nov-Mar.

C. helmsii seems to be most closely related to C. moschata and somewhat resembles a depauperate state of that sp. because, although similar in their proportions, the lvs and fl. parts are smaller than in typical C. moschata. When growing submerged, C. helmsii sometimes has long stems with long internodes. The sp. is naturalised in Britain and is now threatening the indigenous flora of many waterways there (Pain, S., New Scientist 1570: 26 (1987). It was treated as Tillaea helsmii Kirk by Allan (1961).