What does it look like?
Entirely submerged, bottom-rooting perennial with slender rhizomes and roots. Broadly oval leaves (<6x4 cm) clasping the stem are thin, translucent, greenish-brown, slightly wavy at the margins, and arranged alternately on the branched stems (2-3 m long). Small, green flowers on dense spikes (3 cm long) are produced at the water surface from November to January.
Are there any similar species?
Potamogeton crispus and four native Potamogeton species are similar, but none have wavy-edged leaves.
Why is it weedy?
Tolerant of sandy to muddy sediments, still to fast-flowing, and fresh or brackish water. Reproduces easily.
How does it spread?
Reproduces via seed, stem fragments and rhizomes spread by water, possibly by birds, and by people 'liberating' fish and aquarium contents into waterways.
What damage does it do?
Forms dense beds, shading out smaller native species, and contributing to blockages of waterways and subsequent flooding. Rotting vegetation stagnates water, killing fauna and flora. Could possibly hybridise with native Potamogeton species, causing genetic pollution.
Which habitats is it likely to invade?
Lakes, rivers, streams, drains, ponds; potentially throughout New Zealand.
What can I do to get rid of it?
Notifiable Organism. Any suspected new infestations should be reported to Biosecurity NZ or the regional council.