Egeria
| Common name: | Egeria |
| Scientific name: | Egeria densa |
| Management programme: | Exclusion |
Report this pest!
If you think you have seen this pest, we need to know. Please report it.
Egeria is an invasive freshwater weed that grows fast, lives a long time, and can outcompete native freshwater species. Large clumps of egeria can come free from the underwater meadows where they grow, causing flooding by blocking waterways and drainage. It can also choke hydro turbines.
Egeria shades out smaller native species and prevents seedlings establishing. Its rotting vegetation stops water from flowing, killing plants and animals.
As only male plants are found in Aotearoa New Zealand, no seeds are produced. New plants form from stem fragments that break off — this can occur through human activities involving boats, trailers and other water equipment.
Egeria is found throughout the North Island, with only a few sites in the South Island. It has not been reported in Otago.
- Size: Stems can grow up to five metres long.
- Appearance: Egeria is a slim freshwater plant that grows underwater with long, floating stems. Its leaves are narrow, dark green, and grow in groups of 4 to 6 around the stem at the same level.
- Similar species: Similar to lagarosiphon, elodea and hydrilla.
- Flowers: Three-petalled white flowers with yellow stamens (the male fertilising organ of a flower), that sit on the surface of the water. Egeria is not known to seed in Aotearoa New Zealand.
- Habitats: It grows in mostly still or slow-moving, highly lit underwater sites and survives in a wide range of temperatures.
To prevent egeria from establishing in Otago and negatively affecting economic wellbeing and environmental values, it is in the exclusion programme of the Otago Regional Pest Management Plan (2019–2029).
Egeria is declared an unwanted organism in the National Pest Plant Accord (NPPA). Any species declared a pest under the NPPA cannot be sold or be in a place where plants are being sold. Pest plants cannot be propagated, bred, multiplied, communicated, released, caused to be released, or otherwise spread.
Otago Regional Council will be responsible for controlling the plant if it gets into Otago, most likely in collaboration with the Ministry for Primary Industries, Department of Conservation, Toitū Te Whenua Land Information New Zealand, and land occupiers.
If you think you have spotted egeria, please let us know by reporting it .
Preventing the spread of egeria using the Check, Clean, Dry method is the best strategy, as removal of invasive freshwater pests from our waterways is both difficult and expensive.
Cleaning your craft and gear for biosecurity purposes is an important way to help protect the freshwater environment. Just as regular maintenance keeps your equipment in good condition, biosecurity cleaning keeps lakes and rivers healthy for everyone.
To make sure you are not spreading any aquatic pests, the Check, Clean, Dry method is the best way to keep our waterways pest-free.
Report this pest!
If you think you have seen this pest, we need to know. Please report it.
Exclusion
The exclusion programme aims to stop certain pests that are in very low numbers or in surrounding areas from establishing in Otago.
Check, Clean, Dry
CHECK your gear and remove pests. CLEAN your gear thoroughly. DRY it for 48 hours before moving to another waterway!
Priority pests
Priority pests are plants and animals that pose a serious threat to Otago’s environment, economy, or way of life. ORC focuses on controlling these pests quickly to protect native species, waterways, and farmland.
February 2026
PDF | 640 KB
Egeria is an invasive freshwater weed that grows fast, lives a long time, and can outcompete native freshwater species.
November 2019
PDF | 5 MB
The Otago Regional Pest Management Plan focuses on dealing with harmful pests that impact our environment, economy, and communities. It identifies species like rabbits, wallabies, gorse, and wilding conifers that cause problems on our land. Guided by the Biosecurity Act 1993, the plan works with stakeholders to set rules and controls for managing pests. Through consultation, it aims to protect our region's unique ecosystems and species from the damage caused by these invasive organisms.
