Photo credit: Rose Muir NIEA
Common Names: Curly waterweed, African elodea, Lagarosiphon, oxygen weed, South African oxygen weed, submerged onocotyledon
Habitat: Lakes and slow flowing aquatic systems such as canals, low energy rivers and streams. The plant can grow in water up to 6m deep. In addition to occupying the full water column, plant stands produce dense vegetation on the water surface.
Description: This species acts as an aggressive, invasive, alien plant species in Ireland but it is also regarded as a nuisance weed in its home territory. The leaves, 5-20mm long, are strongly recurved and are borne in whorls of 3 or in a spiral arrangement. The long stem is brittle and easily broken (aiding dispersal). Only female plants are present and all reproduction is by fragmentation or vegetative reproduction.
Due to its rampant growth, it develops rapidly into a tangled mass that blocks out the light and alters the entire ecosystem beneath. As a result, native aquatic plants and invertebrates are unable to survive. The plant also causes significant economic damage by choking up water channels and hydroelectric plants and by impairing boating and other water-based recreational activities. As the species is difficult to eradicate, it is important to prevent it from spreading into other EU countries. EU level action includes a ban on sales and any planting or keeping, including in isolated ponds. Furthermore, a rapid eradication of any new populations is required, to avoid the excessively high costs associated with its management later on. Where the species has become widely spread, appropriate management measures have to be taken.
Origin and Distribution: Originating from southern Africa but the species is now present in Europe and Britain.
Impacts: The plant forms very dense infestations in suitable habitats and is capable of occupying the full water column in waters up to 6m deep leading to significant changes to the ecology for native plants, insects and fish. The species is a serious threat for tourism, angling, boating and other recreational pursuits as well as conservation goals. Due to its rampant growth, it develops rapidly into a tangled mass that blocks out the light and alters the entire ecosystem beneath. As a result, native aquatic plants and invertebrates are unable to survive. The plant also causes significant economic damage by choking up water channels and hydroelectric plants.
How did it get here? Native to South Africa, the species was introduced into Europe as an oxygenating plant for the aquarium trade. It has since established itself in slow-flowing water bodies, lakes and ponds across 11 Member States (Austria, Belgium, France, Germany, Hungary, Ireland, Italy, the Netherlands, Portugal, Spain, and the United Kingdom).
Where is it found in Ireland? Present at a number of sites throughout the island of Ireland.
See the for more information on the distribution of this species in Ireland.
- Promote native species and biodiversity - use alternative, native plants.
- Know what you are buying/growing and source native Irish seed and plants.
- Do not swap plants and cuttings.
- Clean plants before adding to ponds (dispose of water away from water courses).
- Follow control advice and watch out for hitchhikers - inspect new imported purchases for invasive pest and pathogens.
- Clean equipment before moving between waterbodies.
- Never collect plants from the wild.
- Follow the guidelines in the 'Be Plant Wise' Section of this website.
- Report all sightings. Northern Ireland
- Report all sightings Ireland
- NBDC ID Guide
- GBNNSS ID Sheet
- Ireland Risk Assessment
- GB Risk Assessment
- EU Risk Assessment