Egeria densa


Family: Hydrocharitaceae

Origin: South America

Egeria floating in the water.
Egeria produces flowers which float on the water surface. Flowers are to 20 mm across, with 3 white petals.
Photo credit: Richard Old, XID Services, Inc.,

Regional Pest Management Plan (RPMP) status

  • National Pest Plant Accord Species
  • Aotea — Eradication
  • Priority Lakes Tomarata and Rototoa
  • Whole region — Sustained control

View more about the RPMP statuses

General description

Bottom-rooted, submerged, perennial, aquatic herb. Stems are long. Leaves are < 30 x 5 mm, in whorls of four to five. Flowers are white and borne at the water’s surface in November – January.

What you need to know

To help protect our environment:

  • You must not breed, distribute, release or sell egeria. As egeria 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 egeria within the Auckland region.
  • You must destroy any egeria 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.

Auckland Council will control egeria at all sites within the Aotea/Great Barrier Island group where it is known to occur.

If you see egeria anywhere on Aotea/Great Barrier Island group, please report it to Auckland Council at


Static to moderately flowing water bodies < 8 m deep.


Vegetative spread from stem fragments, dispersed by water. Human-mediated dispersal through contamination of machinery and equipment and deliberate plantings.

Impact on environment

Forms dense stands, displacing native aquatic plants and altering the habitat structure of macroinvertebrates and fish. Can lower dissolved oxygen levels, increase sedimentation, and alter the primary production and nutrient cycling capacity of water bodies.


Site Management

Follow up treated areas 3 times per year. Spraying large amounts of aquatic weeds result in plants rotting in the water. This decreases dissolved oxygen in the water and can kill aquatic life. Consider physical control and only spraying regrowth.

Recommended approaches

Physical control

Method: Pull out.

Plant parts requiring disposal: All parts.

Disposal options: Remove to greenwaste or landfill if practical.


Biocontrol is currently not available for this species.

Community agrichemical control recommendations

Certified Handler/Experienced agrichemical user: Foliar spray emergent foliage with 100ml glyphosate green per 10L of water.

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