This herbaceous perennial occurs in two growth forms. Plants with long, flaccid stems grow as submerged aquatics, and are sometimes abundant in clear calcareous water. More rigid, stiffly erect shoots grow as emergents at the edge of lakes and ponds, in swamps or in upland flushes. These may be very robust when growing on deep, eutrophic mud. 0-900 m (Moine Mhor, Easterness), but rare above 400 m.
There is little evidence for any marked change in the distribution of this species, although it has spread as an introduction in some counties.
Circumpolar Boreo-temperate element.