Vallisneria australis

Eel grass

Family: Hydrocharitaceae

Origin: Asia, Australia

Close up of eel grass under water.
It has Long, thick, strap-like leaves. The leaves never extend above the surface.
Photo credit: Paul Champion, NIWA

Regional Pest Management Plan (RPMP) status

  • Aotea — Exclusion
  • Whole region — Sustained control
  • National Pest Plant Accord Species

View more about the RPMP statuses

General description

Bottom-rooted freshwater aquatic. Leaves are strap-like, < 550 x 5 cm and submerged. Male flowers are large, pollen-filled sacs produced at the base of the plant. Female flowers are small, green and produced at the end of a very long, spirally coiled stalk that can extend to the water’s surface.

What you need to know

To help protect our environment:

  • you must not breed, distribute, release or sell eel grass. As eel grass is a National Pest Plant Accord species, these restrictions apply within the Auckland region and across the whole of New Zealand
  • you must not plant eel grass within the Auckland region.
  • you must destroy any eel grass on land that you occupy if it has been planted in breach of the above rules and you are directed to do so by an authorised person.

If you see eel grass anywhere on Aotea/Great Barrier Island group, please report it to Auckland Council at pestfree@aucklandcouncil.govt.nz.

Habitats

Static to moderately fast-moving water bodies < 10 m deep.

Dispersal

Vegetative spread from rhizome fragments. Human-mediated dispersal.

Impact on environment

Forms dense stands which may displace native submerged vegetation. May impede drainage, exacerbate flooding, and impede recreational water uses. Can cause drowning through entanglement.

Control

Site management

Very difficult to control once established.

Recommended approaches

Do not attempt to undertake control of this species on Aotea/Great Barrier Island group. Please report to Auckland Council if seen on Aotea/Great Barrier Island group.

Physical control

Method: Pull out.

Plant parts requiring disposal: All parts.

Disposal options: Remove to greenwaste or landfill if practical.

Biocontrol

Biocontrol is currently not available for this species.

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

Close up of eel grass stem underwater.
It forms dense beds that displace native plants.
Photo credit: Paul Champion, NIWA