A floating fern of canals, ditches, ponds and sheltered bays in lakes and rivers. It is most frequent in calcareous water, or near the sea. It reproduces vegetatively, often producing dense mats, and sporocarps are not uncommon. Generally lowland, but reaching 450 m above Rydal Water (Westmorland).
First recorded in Britain in 1883, this species is much more frequent now than it was in the 1962 Atlas. In some areas populations fluctuate greatly annually. It is widely cultivated and frequently disposed of into the wild.
Native of western N. & S. America; widely naturalised in temperate and southern Europe and elsewhere.
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 660
Count of 10km squares in Ireland: 21
Count of 10km squares in the Channel Isles: 9
Atlas Change Index: 2.76
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.