Eleocharis is a virtually cosmopolitan genus of 250 or more species of flowering plants in the sedge family, Cyperaceae. The name is derived from the Greek words ἕλειος (heleios), meaning "marsh dweller," and χάρις (charis), meaning "grace." Members of the genus are known commonly as spikerushes or spikesedges. The genus has a geographically cosmopolitan distribution, with centers of diversity in the Amazon Rainforest and adjacent eastern slopes of the South American Andes, northern Australia, eastern North America, California, Southern Africa, and subtropical Asia. The vast majority of Eleocharis species grow in aquatic or mesic habitats from sea level to higher than 5,000 meters in elevation (in the tropical Andes).
The genus itself is relatively easy to recognize; all Eleocharis species have photosynthetic stems but no green leaves (the leaves have been reduced to sheaths surrounding the base of the stems). Many species are robust, rhizomatously-spreading plants of lowland tropical wetlands, while many others are small caespitose annual or perennial herbs growing near streams, and still others are intermediate. There are also a number of species that are obligate aquatic species, which usually have submerged, branching stems and often exhibit interesting photosynthetic adaptations, such as the ability to switch between C3 and C4 carbon fixation in response to different environmental stimuli. In all Eleocharis species, the flowers are borne on unbranched terminal spikelets at the apices of stems.
In spite of the diversity of the genus itself, taxonomic characters useful for delimiting species within it are few, and many species are very difficult to tell apart. Many currently recognized species with very wide geographic ranges are highly polymorphic. Some of these species probably contain multiple independently evolving lineages. Because of their difficult nature, many botanists avoid collecting these plants and so many species are under-represented in the botanical record.
One of the best known species is the Chinese water chestnut, Eleocharis dulcis. These plants bear tubers on their rhizomes which may be peeled and eaten raw or boiled. In Australia, magpie geese rely almost exclusively on these tubers for sustenance for a significant portion of the year.
- Eleocharis acicularis (L.) Roem. & Schult. – needle spikerush; dwarf hairgrass
- Eleocharis acutangula (Roxb.) Schult.
- Eleocharis afflata Steud.
- Eleocharis atropurpurea (Retz.) J.Presl & C.Presl – purple spikerush
- Eleocharis baldwinii (Torr.) Chapm.
- Eleocharis bella (Piper) Svenson – beautiful spikerush
- Eleocharis bifida S.G. Smith glade spikerush
- Eleocharis bolanderi A.Gray – Bolander's spikerush
- Eleocharis brittonii Svenson ex Small
- Eleocharis cellulosa Torr. – coastal spikerush, Gulf Coast spikerush
- Eleocharis compressa Sull. – flatstem spikerush
- Eleocharis congesta D.Don
- Eleocharis dulcis (Burm.f.) Trin. ex Hensch. – Chinese water chestnut
- Eleocharis elegans (Kunth) Roem. & Schult.
- Eleocharis equisetoides (Elliott) Torr.
- Eleocharis filiculmis Kunth
- Eleocharis geniculata (L.) Roem. & Schult. – Canada spikesedge
- Eleocharis halophila Fernald & Brackett – saltmarsh spikerush
- Eleocharis kuroguwai Ohwi
- Eleocharis macrostachya Britton – pale spikerush
- Eleocharis montana (Kunth) Roem. & Schult.
- Eleocharis montevidensis Kunth – sand spikerush
- Eleocharis mutata (L.) Roem. & Schult. – scallion grass
- Eleocharis nodulosa Schult.
- Eleocharis obtusa (Willd.) Schult. – blunt spikerush
- Eleocharis pachycarpa Desv. – black sand spikerush
- Eleocharis pachystyla (C.Wright) C.B.Clarke – false junco
- Eleocharis palustris (L.) Roem. & Schult. – common spikerush
- Eleocharis parishii Britton – Parish's spikerush
- Eleocharis parvula (Roem. & Schult.) Link ex Bluff et al. – dwarf spikerush, hairgrass
- Eleocharis pellucida J.Presl & C.Presl
- Eleocharis quadrangulata (Michx.) Roem. – squarestem spikerush
- Eleocharis quinqueflora (Hartmann) O.Schwarz – fewflower spikerush
- Eleocharis radicans (A.Dietr.) Kunth – rooted spikerush
- Eleocharis rostellata (Torr.) Torr. – beaked spikerush
- Eleocharis sellowiana Kunth
- Eleocharis tenuis (Willd.) Schult. – slender spikerush
- Eleocharis torticulmis S.G.Sm. – twist-stem spikerush
- Eleocharis tortilis (Link) Schult. – twisted spikerush
- Eleocharis tuberculosa (Michx.) Roem. & Schult.
- Eleocharis uniglumis (Link) (Link) Schult., 1824
- Eleocharis vivipara Link – umbrella hairgrass
- "Genus: Eleocharis R. Br.". Germplasm Resources Information Network. United States Department of Agriculture. 2010-03-03. Retrieved 2013-05-03.
- Kew World Checklist of Selected Plant Families
- Smith, S. Galen; Jeremy J. Bruhl, M. Socorro González-Elizondo & Francis J. Menapace. "ELEOCHARIS R. Brown, Prodr. 224. 1810.". Flora of North America. eFloras.org. Retrieved 2013-05-03.
- Govaerts, R. & Simpson, D.A. (2007). World Checklist of Cyperaceae. Sedges: 1-765. The Board of Trustees of the Royal Botanic Gardens, Kew.
- Flora of North America, Vol. 23 Page 4, 6, 7, 29, 60, Eleocharis R. Brown, Prodr. 224. 1810.
- Flora of China, Vol. 23 Page 188, 荸荠属 bi qi shu, Eleocharis R. Brown, Prodr. 224. 1810.
- Altervista Flora Italiana, genere Eleocharis includes photos plus distribution maps for Europe and sometimes for North America
- Biota of North America Program, 2013 county distribution maps for US and Canadian species
- "Eleocharis". Integrated Taxonomic Information System. Retrieved 2013-05-03.
- "GRIN Species Records of Eleocharis". Germplasm Resources Information Network. United States Department of Agriculture. Retrieved 2013-05-03.
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- USDA Plants Profile: North American Species
- eFloras Profile
- Baksh & Richards (2006) An architectural model for Eleocharis: morphology and development of Eleocharis cellulosa (Cyperaceae). Am J Botany 93:707-15.
- Rataj, Karel. 1977. Aquarium plants; hair grass. TFH 12/77.