This pondweed was accidentally introduced into Ireland from North America. The first ever report of its occurrrence anywhere in Europe was at Waringstown, Co. Down in 1836. It subsequently spread at a tremendous rate across Ireland and Great Britain and is now extremely common in lowland lakes, ponds, canals and slow rivers.
The two sexes are on separate plants. The spread is entirely by vegetative means because only female plants occur in the British Isles, so seed-set is impossible.
All names: Elodea canadensis Michaux
NBN Atlas mapping: Species account : NBN Atlas UK Species Observations database
iNaturalist: Species account : iNaturalist World Species Observations database