Vascular – Exotic
Herbs - Monocots
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
Bottom rooted aquatic perennial plant with different submerged leaves (strap like) on juvenile plants and floating leaves on mature plants. Floating leaves are typically green with dark green veins. The distinct flowers have only three white petals with a dark red/purple base and orange stamens.
Locally common in the North Island but also in northern South Island.
It may occur in slow moving water and on the margins and shallow water of large lakes, but is more commonly found in fertile farm ponds and small lakes.
Wetland plant indicator status rating
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
This bottom rooted plant has basal leaves; the submerged leaves are strap like, and those that float on the water surface have a long petiole. The floating leaves lie flat on the water surface and are oval to football shaped, 2 to 16 cm long, with 5 to 7 longitudinal nerves veins that are more prominent on the lower surface than on the upper. These veins are normally darker green than the remainder of the leaf. The flowers occur on stout peduncles and are of two kinds, those which remain unopened and submerged on short peduncles and those that are conspicuous and emergent. The latter flowers are large (c. 5cm across) and emergent on peduncles up to 38 cm long, each flower has 3 sepals with 3 alternate petals. The petals are white (to cream) with a dark red/purple base, rounded and creased lengthwise (a little like crepe paper). The anthers are yellow/orange and conspicuous. Flower stalks bend downwards into the water when fertilised. The fruit remains attached to the plant as the seed ripens. The fruit wall eventually disintegrates to release the seed, which is narrow/oval 2.5 to 3 mm long and has numerous fine appressed hairs.
The strap like leaves of young plants may be mistaken for Vallisneria australis or Sagittaria spp., and the surface floating leaves for Cape pondweed (Aponogeton distachyos) or the native red pondweed (Potamogeton cheesemanii). Both vallisneria and sagittaria are stoloniferous. Vallisneria flowers are not 3-petalled. Sagittaria does have 3-petalled white flowers, but do not have floating leaves. Capre pondweed has narrower, longer leaves and neither this or red pondweed have dark green veins and a lighter coloured leaf, or 3-petalled white flowers.
December - March
Perennial. Reproduces from seed, no tubers, rhizomes or runners. Water fowl feed on fruit and disperse seed and also seeds may be dispersed by water movement.
Reason for introduction
Unknown, possibly introduced from Australia by waterfowl or via contaminated drainage machinery.
Not controlled in New Zealand.
Tolerant of hot-cool temperatures
Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA).
References and further reading
Johnson PN, Brooke PA (1989). Wetland plants in New Zealand. DSIR Field Guide, DSIR Publishing, Wellington. 319pp.
Aston, H (1977). Aquatic plants of Australia. Melbourne University Press, 367pp.
Coffey BT, Clayton JS (1988). New Zealand water plants: a guide to plants found in New Zealand freshwaters. Ruakura Agricultural Cente. 65pp