A rhizomatous perennial of still or slow-flowing water in lakes, rivers, canals, ditches and flooded mineral workings. P. alpinus is often found in sites where silt accumulates, such as lake inflows or backwaters in rivers. It characteristically grows in mesotrophic, often neutral or mildly acidic water. 0-945 m (Meall nan Tarmachan, Mid Perth).
Many of the sites from which P. alpinus has been lost in England are small ponds, pits and ditches where it was last seen in the 19th century. There have been some further losses in England and S.E. Scotland from eutrophication, but the distribution elsewhere appears to be stable.
Circumpolar Boreal-montane element.
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