Triangular club-rush (Schoenoplectus triqueter)

GenusSchoenoplectus (1)
SizeHeight: 50-150 cm (2)

Classified as Critically Endangered in Great Britain and fully protected under Schedule 8 of the Wildlife and Countryside Act 1981 (3).

Triangular club-rush is a critically endangered species in Britain. Both the common name and the Latin name triqueter (from the Latin triquetrus meaning three-cornered) (4) refer to the cross-sectional shape of the hairless stems, which have three corners (2). The plant mainly spreads by means of creeping rhizomes in Britain (5), and produces flowers at the top of the stem in groups called spikelets, which are in turn arranged in clusters known as inflorescences (2).

This species was first found in 1650 on the River Thames (6), and it has since been recorded from several sites, all in the south of England, including the River Medway in Kent, the Tamar in Devon and Cornwall, and the Arun in West Sussex. Following a severe decline the species is now known only from the River Tamar in Devon, where it exists as just one or two small clumps (5). In Ireland it has been recorded in three rivers, and although gone from one river, it still has a large and apparently stable population on the Shannon (5).

It is a very widespread species, which is locally abundant in the tropics and becomes rarer further north. It is recorded from west, central and southern Europe through western, central and eastern Asia to Japan and the Philippines, and in north Africa (recorded once on the Suez canal only) and South Africa. It is so prolific in some areas that control with herbicides is required. It occurs from sea-level in many parts of the world to an altitude of at least 2400 m in Kashmir (5).

In Britain and Ireland it is restricted to the upper parts of tidal rivers where there are weakly brackish to fresh water conditions and large fluctuations in water level (at very high tides the plants may be submerged), but it occurs in a variety of wetlands and fresh water ecosystems elsewhere in the world (5). It is even a weed of paddy fields in Asia (5).

Triangular club-rush is a perennial species (6) that seems to be able to tolerate brackish (slightly salty) water, but may fare better if freshwater flows around the rhizomes (3). It rarely produces seed in the wild in Britain and Ireland, but does so readily in cultivation and in Europe (and probably elsewhere) (5).

The three main causes of the decline in Britain appear to be direct loss of habitat due to construction of river embankments, growth of common reed, and failure to recolonise after indirect changes in the river flow patterns resulting from river engineering, canalisation, etc., which cause erosion of the river banks and the subsequent loss of colonies (5). Increased flow rates resulting from extensive drainage of the catchments may contribute to changing water flows. Furthermore, increased sedimentation rates due to high sediment runoff from ploughed fields may have changed deposition and erosion patterns. There is no direct evidence that water pollution, wash from boat traffic, collection by botanists or hybridisation has caused decline. The species is probably not under threat world-wide (5).

Triangular club-rush is a UK Biodiversity Action Plan priority species, and a Species Action Plan has been produced to coordinate conservation efforts. The Environment Agency is the lead partner for this species and has carried out a number of measures with English Nature and Royal Botanic Gardens Kew, including the enhancement of the remaining plants on the River Tamar. In addition an ex-situ programme has been established at Royal Botanic Gardens, Kew (6). Future plans include continued monitoring, and genetic studies to investigate whether reintroduction programmes are suitable (6).

For more on this species see the book: New Atlas of the Flora of Britain and Ireland, by Preston, C. D., Pearman, D. A., Dines, T. D. (2002). Published by Oxford University Press, London.

Visit the website of the Botanical Society of the British Isles at:

Information authenticated by Tim Rich of the National Museums and Galleries of Wales.

  1. National Biodiversity Network Species Dictionary (March, 2002)
  2. Clapham, A.R., Tutin, T.G. and Moore, D.M. (1987) Flora of the British Isles. 3rd Ed. Cambridge University Press, Cambridge.
  3. UK BAP Species Action Plan (March, 2002)
  4. (March, 2002)
  5. Rich, T.C.G. and Fitzgerald, R. (2002) Life cycle, ecology and distribution of Schoenoplectus triqueter (L.) Palla (Cyperaceae), Triangular club-rush, in the British Isles. Watsonia, 24: 57 - 67.
  6. Environment Agency. (1998) Focus on Biodiversity. The Environment Agency, Bristol.