Carex aquatilis

Tracheophyta MagnoliopsidaCyperaceaeCarexCarex aquatilis


A morphologically variable, rhizomatous perennial. In the lowlands, robust plants grow on river banks and the margins of lakes, mires and reed-swamps. In its upland sites, it is a shorter plant and often grows on deep, wet, gently sloping peat. 0-975 m (Glas Maol, Angus).



World Distribution

Circumpolar Boreo-arctic Montane element; absent from mountains of C. Europe.

© Pete Stroh

Broad Habitats

Light (Ellenberg): 8

Moisture (Ellenberg): 10

Reaction (Ellenberg): 4

Nitrogen (Ellenberg): 3

Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 2.3

July Mean Temperature (Celsius): 13.2

Annual Precipitation (mm): 1255

Height (cm): 110

Perennation - primary


Life Form - primary

Perennial hydrophyte (perennial water plant)

Life Form - secondary




Clonality - primary

Rhizome far-creeping

Count of 10km squares in Great Britain: 219

Count of 10km squares in Ireland: 39

Count of 10km squares in the Channel Isles: 0

Atlas Change Index: 0.76

JNCC Designations


Scarce Atlas Account

Scarce Atlas Account: 

Carex aquatilis Wahlenb.

Water sedge

Status: not scarce


This is a species of mires and swamps. In lowland lake basins it frequently forms large stands with Carex rostrata, C. vesicaria and Equisetum fluviatile at the upper end of the basin. It can be dominant in swamps alongside slow-flowing rivers, with Carex acutiformis, C. vesicaria, Phalaris arundinacea and Phragmites australis. In upland areas it is found on gently sloping mires on deep peat, with Carex curta, C. nigra, C. rariflora, C. rostrata and several Sphagnum species and bryoid mosses. It also occurs by drainage channels in upland mires and occasionally alongside fairly fast flowing upland rivers. In these habitats plants are notably shorter than those in the lowlands. It has a wide altitudinal range from sea-level to 750 metres on Glas Maol.

It is a rhizomatous perennial. The rhizome is far-creeping and the plant therefore has a considerable potential for vegetative spread. Plants are often sterile over large areas, especially where populations are shaded or where there have been changes in water level. C. aquatilis is wind pollinated and hybridises readily with other members of the C. nigra group. Many populations appear to be hybrid swarms.

Some lowland populations are disappearing due to land-use changes, but those in the Scottish Highlands are not threatened except very locally in areas selected for ski developments where ski-tows and downhill running could be detrimental.

This is a circumpolar species. In Europe it extends south to Wales, northern Germany and central Russia but in western North America it occurs as far south as Arizona and California.


A. C. Jermy

Atlas text references

Atlas (364c)
Hultén E, Fries M
1986.  Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jermy AC, Chater AO, David RW
1982.  Sedges of the British Isles. Botanical Society of the British Isles Handbook no. 1, edn 2.
Preston CD, Croft JM
1997.  Aquatic plants in Britain and Ireland.
Stewart A, Pearman DA, Preston CD
1994.  Scarce plants in Britain.