Species

Potamogeton perfoliatus

Etymology

Potamogeton: river dweller

Common Name(s)

clasped pondweed

Authority

Potamogeton perfoliatus L.

Family

Potamogetonaceae

Brief Description

Submerged aquatic plant that has green to red/brown leaves arranged alternately on stems, with the base of the leaves 'clasping' the stem. The leaves are up to 7cm long and 4cm wide with undulating margins, distinct longitudinal veins and finer transverse ones.

Flora Category

Vascular - Exotic

Structural Class

Monocotyledonous Herbs

Distribution

Eradicated, only known from three sites, near Lakes Wakatipu and Hayes, Otago and Christchurch.

Habitat

Moderate flowing to still water bodies.

Features

Entirely submerged, bottom-rooting, normally perennial. Slender rhizomes and roots. The stems are up to 2m long, and the leaves clasp the stem. Alternate leaves are narrow to broadly ovate and greater the 6mm wide (although variable in size), green to red/brown in colour, thin and translucent, with undulating margins and many longitudinal veins and finer transverse venation. The inflorescence spike is short (1 to 2 cm long) when in fruit. Flowers small, green, on dense spikes up to 3 cm long at water surface. The fruit are 2.5 to 3 cm long, olive-green and smooth, convex on the ventral side and semi-circular on the dorsal. The keel is faint, as are 2 lateral ridges on the dorsal side and the beak is very short.

Similar Taxa

Potamogeton perfoliatus can be distinguished from all other potamogetons by the way the leaf clasps the stem.

Flowering

November - January

Flower Colours

Green

Fruiting

Not seen in New Zealand

Year Naturalised

1996

Origin

Native to Central and North America, Eurasia, Africa and Australia

Reason for Introduction

Ornamental pond and aquarium plant

Control Techniques

Notify Ministry for Primary Industries if found.

Life Cycle and Dispersal

Reproduces by stem fragments and seeds. Dispersed by water, people liberating fish, possibly birds.

Tolerances

Tolerant of sandy to muddy sedinments, still to fast flowing , fresh or brackish water.




Attribution

Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA).

References and further reading

Champion et al (2012). Freshwater Pests of New Zealand.  NIWA publication. http://www.niwa.co.nz/freshwater-and-estuaries/management-tools/identification-guides-and-fact-sheets/freshwater-pest-species.

Aston, H (1977).  Aquatic plants of Australia. Melbourne University Press, 367pp.; Sculthorpe (1967) the biology of aquatic vascular plants.  Edward Arnold Press, London. 

This page last updated on 21 Aug 2013