Eleocharis, commonly called spikerushes or spikesedges, is a large genus of about 250 or more species (with 573 accepted taxa including infraspecific ranks per GBIF) in the sedge family Cyperaceae, order Poales. The genus was described by Robert Brown and published in his Prodromus Florae Novae Hollandiae in 1810. Its name derives from the Greek heleios ("marsh dweller") and charis ("grace"), reflecting the characteristic habitat of its members.
Unlike most flowering plants, Eleocharis species perform photosynthesis through their stems rather than leaves — the leaves are reduced to non-photosynthetic basal sheaths wrapped around the stem base. This adaptation to waterlogged, anaerobic soils is taken furthest in aquatic forms, which develop submerged branching stems and, remarkably, some species can switch between C3 and C4 carbon fixation pathways depending on environmental conditions.
The genus is cosmopolitan in distribution, occurring on every inhabited continent with greatest diversity in the Amazon basin and adjacent Andean slopes, northern Australia, eastern North America, California, southern Africa, and subtropical Asia. Species occupy a wide elevational range from sea level to above 5,000 metres, always associated with wet ground: marshes, fens, lake margins, river banks, rice paddies, and seasonally inundated flats.
The most economically significant member is Eleocharis dulcis, the Chinese water chestnut, whose starchy corms are a staple ingredient across East and Southeast Asian cuisines. Other species play important ecological roles in wetland communities worldwide, providing cover and food for waterbirds and other wetland fauna.
Etymology
The genus name Eleocharis is formed from two Greek words: heleios (ἕλειος), meaning "marsh dweller," and charis (χάρις), meaning "grace." The name was coined by the Scottish botanist Robert Brown when he formally described the genus in 1810 in his Prodromus Florae Novae Hollandiae et Insulae Van Diemen. The epithet aptly captures the graceful, rush-like appearance of plants that inhabit swamps, fens, and other wetland margins across the world. Historical synonyms for the genus include Heleocharis, a Latinized spelling variant of the same Greek roots, as well as Baeothryon and around 14 other names reflecting the genus's long and complex taxonomic history.
Distribution
Eleocharis is cosmopolitan, present on every inhabited continent. Its global centres of species diversity are the Amazon rainforest and adjacent eastern slopes of the South American Andes, northern Australia, eastern North America, California, southern Africa, and subtropical Asia. Species range in elevation from sea level to above 5,000 metres, growing wherever suitable wet habitats persist.
In Europe, Switzerland alone supports 11 species including E. acicularis (needle spike-rush), E. palustris (marsh spike-rush), E. quinqueflora, E. uniglumis, E. carniolica, and E. atropurpurea, distributed across lowland fens, alpine mires, and lake shores. Eleocharis dulcis is native to tropical Africa and East Asia, where it is cultivated across China, Japan, India, and Southeast Asia in paddies and marshy fields.
Taxonomy
Eleocharis belongs to the family Cyperaceae (the sedge family) within the order Poales. The accepted author citation is R.Br. (Robert Brown, 1810). ITIS assigns the genus Taxonomic Serial Number 40010. GBIF records 573 accepted descendants encompassing species and infraspecific taxa, while traditional species counts in the literature cite approximately 250 or more species — the discrepancy reflects the inclusion of subspecies and varieties in the GBIF total.
The genus has accumulated around 16 synonyms including Heleocharis (a common orthographic variant still encountered in older literature), Baeothryon, and others, reflecting extensive historical reclassification. Many nineteenth- and early-twentieth-century names are now regarded as not accepted, and ongoing molecular and morphological work continues to revise species boundaries, particularly within complex polyploid groups. The genus is subdivided into several informal or formally recognised sections based on glume arrangement, style-base morphology, and perianth bristle number.
Ecology
Almost all Eleocharis species grow in aquatic or mesic habitats — marshes, fens, lake and river margins, rice paddies, wet grasslands, seasonally flooded flats, and the edges of mangroves. They tolerate waterlogged, often anaerobic substrates that exclude most competitors.
Aquatic species develop submerged stems that function as photosynthetic organs, and some are physiologically remarkable in their ability to switch between C3 and C4 carbon fixation depending on whether the stems are aerial or submerged, giving the genus scientific interest beyond its economic value. In Swiss and broader European contexts, spikerushes are characteristically associated with the Nanocyperion vegetation alliance — low-growing pioneer communities on seasonally wet, often disturbed, nutrient-poor substrates.
The genus provides important ecosystem services in wetlands: dense stands stabilise sediment, filter nutrients, and provide nesting and foraging habitat for waterbirds. Australian magpie geese, for example, are substantially dependent on the corms of Eleocharis dulcis as a seasonal food source.
Conservation
Several Eleocharis species appear on national Red Lists reflecting habitat loss through wetland drainage, agricultural intensification, and climate-driven hydrological change. In Switzerland, species assessments are documented in the National Red List (2016) and Regional Red List (2019), and ex-situ conservation programmes exist for threatened taxa. The specialized Nanocyperion wetland communities with which many European spikerushes are associated are themselves considered threatened across much of Central Europe.
Cultivation
Eleocharis dulcis is the cultivated member of the genus, grown commercially across tropical and subtropical Asia for its edible corms. It requires marshy ground or shallow standing water, slightly acidic soil, and full sun. Optimal leafy growth occurs at 30–35°C, while tuber formation is favoured at temperatures approximately 5°C cooler; water temperature should remain above 15°C for good corm development. A frost-free growing season of at least seven months is necessary, as the plant does not tolerate freezing.
Commercial yields of 20–40 tonnes of corms per hectare are achievable under optimal management. Plants grow to approximately one metre tall at a fast growth rate. Non-commercial spikerushes are occasionally grown in wildlife or ornamental ponds for their ecological value and fine texture, and several dwarf species (notably E. acicularis) are popular in aquaria and water gardens because they form dense low mats and tolerate a wide range of water depths.
Propagation
Eleocharis dulcis and related cultivated forms are propagated primarily by division of corms. Tubers are harvested at the end of the growing season, stored in cool frost-free conditions, and replanted in early spring when water temperatures rise above 15°C. Seed propagation is also possible: seeds are sown under glass in a minimal depth of water (approximately 3 cm) with light covering, and germination occurs as temperatures rise.
Most wild Eleocharis species spread vegetatively through rhizomes or stolons, forming dense stands; division of established clumps is the standard method for establishing plants in aquatic garden or restoration plantings. Some species also produce bulbils or proliferating spikelets that facilitate passive dispersal.
Cultural uses
The most important cultural use of the genus centres on Eleocharis dulcis, the Chinese water chestnut, whose corms have been harvested and cultivated in East and Southeast Asia for centuries. The corms are eaten raw or cooked — sweet and crisp when fully ripe — and are a standard ingredient in Chinese cuisine, featuring in dishes such as chop suey. Ground dried corms yield a flour used to thicken sauces and as a coating for deep-fried foods. Dried corms contain approximately 36% starch and yield around 360 calories per 100g.
Beyond food, the juice of the corms has documented antimicrobial properties: it contains the compound puchiin, which is active against Staphylococcus aureus, Escherichia coli, and Aerobacter aerogenes. Traditional medicine systems in the region use the plant to treat abdominal pain and liver disorders. In Southeast Asia, the fibrous leaf stems are woven into bags and mats, and the plant biomass serves as cattle fodder and mulch. Wetland stands also contribute to water quality improvement in managed wetland systems.
