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).
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).
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).
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).
A group of organisms living together, individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or ‘individuals’), which are produced by budding and remain physiologically connected.
The government agency that champions the conservation of wildlife and natural features throughout England.
Measures to conserve a species or habitat that occur outside of the natural range of the species. E.g. in zoos or botanical gardens.
The reproductive shoot of the plant, which bears flowers.
Plants that live for at least three seasons; after an initial period they produce flowers once a year.
Rhizomes are thickened, branching, creeping storage stems. Although most rhizomes grow laterally just along or slightly below the soil’s surface, some grow several inches deep. Roots grow from the underside of the rhizome, and during the growing season new growth sprouts from buds along the top. A familiar rhizome is the ginger used in cooking.
The Environment Agency
The government organisation responsible for pollution control and water resources management including flood defence, fisheries and navigation in England and Wales.
Embed this ARKive thumbnail link ("portlet") by copying and pasting the code below.