Canadian waterweed

Elodea canadensis


  • Photo credit: ©Robert Vidéki/Doronicum Kft./

  • Canadian waterweed - Elodea canadensis

  • Description: It is a perennial submerged plant, with long flexible stems. The leaves are mildly serrated and are whorled into nodes on the stems. White flowers are either male or female with female flowers measuring 2-3mm and male flowers reaching 5mm in length. It can spread vegetatively as there are only female plants currently in Europe. It is highly adaptable, and survive in a wide range of climate and water nutrient conditions.

Download N.I.E.A ID guide

  • Origin and Worldwide Distribution: It comes from North America, indigenous in the Great Lakes and the Pacific West Coast, but spreading throughout the USA. It was introduced to the UK in the 19th century, ad is present in Egypt, Morocco, South Africa, Turkey, Israel, Austria, Belgium, Bulgaria, Denmark, Estonia, Finland, France, Germany, Hungary, Ireland, Italy, Latvia, the Netherlands, Norway, Poland, Portugal, Russia, Spain, Switzerland, Australia, New Zealand and Ukraine. 

  • Potential or Known Impacts: It produces single species stands, which outcompete native plants for nutrients and space. This leads to a decrease in biodiversity. These stands reduce water movement and produce anoxic conditions. It also has a negative impact on the boating and fishing communities as they are unable to access and use waterways safely.

  • How did it/could it get here? It had been intentionality introduced as an aquarium plant outside its native range, and has spread by being dispersed with garden waste, and escaping from garden ponds. It can also spread by boats, fishing equipment and clothing if they haven’t been checked and cleaned between visiting different sites.

  • Is it found in Northern Ireland? It is found in Northern Ireland.

You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
Methods for Prevention:
  • Boats, fishing equipment, and clothing should be checked for small parts, and cleaned off if there are any present to prevent it being spread into new locations.
  • Mechanical control can be used in the form of specialised barges, and cutting machines on boats and tractors. Care needs to be taken to ensure that fragments aren’t dispersed further downriver.
  • Report all sightings.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email:  

Species Related Files:

Invasive Species Ireland

Invasive Species Ireland