Clasped Pondweed

Europe and Canada

General description

Submerged freshwater aquatic plant that occurs in still and flowing water. The most characteristic feature is the way the leaves wrap around the stem. Stems long, trailing, leafy. Leaves are very thin, wavy margins (narrow-broadly ovate >6 mm wide), appear translucent, pale green or bronze. Flowers and fruit in summer and autumn on a short spike floating on the surface.

Lakes, ponds, rivers and streams. Can also tolerate brackish water.

Stem fragments and seed spread by water, contaminated machinery, boats, trailers and nets. Also people 'liberating' fish, possibly birds.

Clasped pondweed is an invasive weed that poses a serious threat to New Zealand waterways if allowed to establish here. It has the potential to hybridise with native Potamogeton species.

Site management

Notifiable Organism. Any suspected new infestations should be reported to MAF or the Auckland Regional Council. Every attempt should be made to eradicate this rare weed.

Recommended approaches

1. Bottom lining: controls patches but reseeding may occur. Begin at upstream end of infestation and work down, 3-4 months per section.
2. Grass carp. Do not use, except under special circumstances, refer DoC policy.
3. Lower water level, mechanically remove or use weedmat.
4. Suction removal. Mulch. Work methodically to trap all fragments, ensure collection bags do not leak. Water flow can assist to shift infestation boundary down stream.

Caution: when using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

Search tags

RPMS status

Surveillance - Whole Region
National Pest Plant Accord species - nationwide
clasped pondweed - Main species image