An annual aquatic plant, sometimes overwintering as a rosette, growing on silt, gravel or stony substrates in acidic, oligotrophic lakes. It is normally a plant of water shallower than one metre, and is only rarely found in other water bodies, such as outfall streams. 0-825 m (Ffynnon Llyffaint, Caerns.).
Because of better exploration, S. aquatica is now known from many more sites than were mapped in the 1962 Atlas. However, eutrophication seems to have caused declines along the eastern fringe of its range, and also in the Lake District and N. Ireland.
Circumpolar Boreal-montane element, with a disjunct distribution.
Perennation - primary
Life Form - primary
Comment on Life Form
Clonality - primary
Count of 10km squares in Great Britain: 324
Count of 10km squares in Ireland: 33
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.73
Scarce Atlas Account
Subularia aquatica L.
Status: not scarce
This rooted aquatic plant is typically found in oligotrophic and base-poor lakes. However, on Skye it is found in a few sites of a higher base status which are located on basalt but which also receive some acid influence. It usually occurs in shallow water (less than 1 metre), although in clear water it may grow at greater depths. Plants are often isolated or in small groups of two to three and are commonly found growing amongst Littorella uniflora. It is usually found on rocky substrates and may grow between stones and boulders, although it also occurs less commonly on silt and on sandy substrates. It is found in lochs with a peaty influence, although it is generally absent from peaty pools. In Scotland, it has been found as low as 5 metres altitude (Loch Hope and Loch Evelix) and up to 795 metres (Sandy Loch and the Cairngorms).
This is an annual plant, which is usually self-pollinated.
Owing to its small size and superficial similarity to Littorella uniflora, S. aquatica has been poorly recorded in the past and is commoner than was once supposed. During survey work in the north of Scotland conducted by the Nature Conservancy Council freshwater loch survey team, S. aquatica was found in many new sites, and it no longer qualifies as nationally scarce, In areas which have not yet been covered by this project it is probably still under-recorded.
Abroad it is known from the mountains of western Europe and in northern Europe from Ireland and Scandinavia to northern Russia; also from Siberia, Greenland, and North America.
For a more detailed description of the ecology of this species, see Woodhead (1951).
S. L. Bell
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.
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1996)
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
1997. Aquatic plants in Britain and Ireland.
1991. Crucifers of Great Britain and Ireland. Botanical Society of the British Isles Handbook no. 6.
1994. Scarce plants in Britain.