Nuttalls waterweed

Habitat: E. nutallii is most common in calcareous waters and eutrophic waters because it has a high tissue demand for both phosphorus and nitrogen.

Similar Species: Elodea canadensis

Description: Elodea nuttallii originated from North America. This species is very similar to another invasive specie know as Elodea canadensis (Canadian waterweed). Both species grow in still or slow flowing eutrophic waters but Elodea nuttallii has replaced E. canadensis at many sites possibly due to increased eutrophication. This is an aquatic weed that grows rapidly towards the surface of eutrophic freshwater systems without branching where they form a densely branched canopy. E. nuttalli is perennial and over winters in Ireland as horizontal shoots which regenerate new lateral shoots as the temperature reaches 6-8°C.

Origin and Distribution: This species is native to North America but is now invasive in Britain where it is common.

Impacts: E. nuttallii tends to dominate native macrophyte communities which may lead to there local extinction. Impacts have also been recorded on invertebrate communities. This species may also have a significant impact on protected sites. E. nuttallii is also known to replace other invasive species as the dominant species in an impacted ecosystem. More recently data from Britain suggests that this species is now becoming replaced by Largarosiphon major.

How did it get here? Traded as a garden plant.

Where is it found in Ireland? This species now occurs at a number of sites spread right across the island

• 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
• Safe disposal of plant material and growing media