A semi-evergreen perennial spreading vegetatively by very long thin rhizomes to form large colonies in permanently wet places on organic (less commonly, mineral) soils. Habitats include river banks and streamsides, marshes, tall-herb fens, fen-carr, ponds and ditches. It withstands some shade in wet open woodland. Lowland.
This species was mapped as `all records` in the 1962 Atlas. Analysis of the database reveals that most losses, resulting from drainage and the clearance of watercourses, have taken place since 1950. It can, however, readily colonise suitable new sites, perhaps assisted by waterfowl.
Eurasian Temperate element; widely naturalised outside its native range.
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