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Eleocharis torticulmis

(Twisted Spikerush)


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Critically Endangered

Threat status

Common Names

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Common Names in English:

Twisted Spikerush


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Family Cyperaceae

Herbs, annual or perennial , cespitose or not, rhizomatous or not, stoloniferous or not. Roots fibrous , principally adventitious. Stems (culms ) usually trigonous , occasionally terete , rarely compressed , usually solid, rarely hollow or septate . Leaves basal and/or cauline, alternate, usually 3-ranked, rarely 2-ranked or multi-ranked, bases forming cylindric sheaths enclosing stem, margins usually fused; junction of sheaths and blades often with adaxial flaps of tissue or fringes of hair (ligules) ; blades frequently absent from some basal leaves , rarely from cauline leaves, when present divergent or ascending , flat, folded, plicate , rolled, or terete, linear , venation parallel. Primary inflorescences (spikelets ) a shortened axis; glumaceous bracts (scales ) 1-many, spirally arranged , sometimes 2-ranked, usually appressed or ascending; scales usually all fertile , each subtending a single flower, sometimes proximal and/or distal scales empty; lateral spikes often with basal, usually empty, usually 2-keeled scale (prophyll) ; occasionally prophyll subtending and enclosing rachilla, bearing 1 pistillate , sometimes (0-) 3 staminate flowers and empty scales (Carex, Cymophyllus, and Kobresia) . Secondary inflorescences panicles, often modified to corymb, pseudoumbel, cyme (anthela), raceme , spike, or capitulum (head ), rarely single spike, usually subtended by foliaceous or, less frequently, glumaceous bracts; secondary inflorescences sometimes simulating spikelets (Carex, Cymophyllus, and Kobresia) . Flowers hypogynous, bisexual in most genera, unisexual in Scleria, Carex, Cymophyllus, and Kobresia; perianth absent or with (1-) 3-6(-30) bristles and/or scales, usually falling off with fruit; stamens usually (1-) 3, rarely more, usually distinct ; anthers basifixed ; pistils 1, 2-3(-4) -carpellate, fused, locule 1; style undivided or branches 2-3(-4) ; stigma sometimes papillate . Fruits achenes, usually trigonous or biconvex ; pericarps thin (except in Scleria) . Seeds 1; testa thin, free from pericarp; embryo basal; endosperm abundant. x = 5-ca. 100.

Genera ca. 100, species ca. 5000 (27 genera, 843 species in the flora ) : worldwide.

No consensus exists regarding the number of genera and the overall relationships of genera within Cyperaceae. The most recent account of the family (P. Goetghebeur 1998) recognized 104 genera distributed among 4 subfamilies and 14 tribes . That arrangement differs somewhat from that of J. Bruhl (1995) . With one minor exception the arrangement of the family here follows that of Goetghebeur.

The family is characterized by the occurrence of a number of unusual cytological features including: (1) chromosomes with diffuse centromeres , (2) post-reductional meiosis, and (3) pollen grains formed from tetrads in which 3 of the 4 microspores fail to develop. The first two features are found in at least some Juncaceae and are unique to the two families. Juncaceae also have pollen in tetrads, but in that family all four microspores produce pollen grains. Some species in some genera of Cyperaceae (particularly Eleocharis) possess chromosomes with localized centromeres (S. S. Bir et al. 1993) . The wide range of chromosome numbers found in Cyperaceae is largely because of agmatoploidy; polyploidy has been hypothesized for some genera, especially Eleocharis, although polyploidy has not been demonstrated unequivocally.

Because of morphologic similarities in vegetative and inflorescence characters, the family has commonly been associated with Poaceae. Cytological features discussed above clearly indicate that to be a superficial similarity . Data from rbcL studies also support the view that Cyperaceae and Poaceae are not closely related (M. R. Duvall et al. 1993b; G. M. Plunkett et al. 1995) ; they do support the concept of close relationship between Cyperaceae and Juncaceae.

For most families of flowering plants the phenological data given are flowering times. Because most Cyperaceae cannot be reliably identified when in flower, in this volume fruiting time is given for all species by season , sometimes qualified by early, mid, or late, or by months. The fruiting time has been interpreted broadly to include the period when the fruit is more or less fully formed but not yet ripe . The fruiting period provided covers the entire range of the taxon . Quite a difference between fruiting periods in different parts of the range of the species may well occur, especially for widespread species and species with extensive elevation range.

For a recent, comprehensive review of the economic importance of Cyperaceae, see D. A. Simpson and C. A. Inglis (2001) .[1]

Genus Eleocharis

Herbs, annual or perennial , usually cespitose, often rhizomatous , sometimes stoloniferous ; rhizomes rarely with terminal tubers or bulbs, horizontal and long or ascending and caudexlike. Culms sometimes solitary, terete , 3-5-angled or more, or strongly compressed in cross section , spongy with internal air cavities and incomplete transverse septa or sometimes hollow with complete transverse septa. Leaves basal, 2 per culm; ligules absent; blades absent or a mucro or awn (tooth ) at apex of sheath , very rarely flattened, to 6 cm. Inflorescences terminal; spikelet 1; involucral bracts absent, rarely a proximal scale of spikelet resembling short bract. Spikelets: scales 4-500 or more, spirally or rarely distichously arranged, each subtending flower or proximal 1-2(-3) empty, stramineous (straw-brown) to medium brown or red brown or blackish brown. Flowers bisexual ; perianth of (0-) 3-6(-10) bristles , straight or curved , shorter than to 2 times longer than achene, retrorsely (to antrorsely) spinulose or sometimes smooth ; stamens 1-3; styles linear , 2-3-fid, base (tubercle) usually persistent , usually enlarged, usually different in appearance from achene. Achenes biconvex , plano-convex , or trigonous to subterete.

Species ca. 200: worldwide.

The name of the genus has sometimes been given as Heleocharis Lestibudois; this is now regarded as an orthographic variant of Eleocharis.

Eleocharis dulcis (Burman f.) Trinius ex Henschel is sometimes cultivated for its edible tubers. Some species are weeds in rice fields , mostly extraterritorially. Almost all species are restricted to wetlands, often emergent, and sometimes submerged aquatic .

No recent comprehensive worldwide taxonomic treatment of Eleocharis is available. The treatment herein is based mostly on the extensive studies by H. K . Svenson (1929, 1932, 1934, 1937, 1939, 1947, 1957), which were mostly restricted to species of North America. Classification of Eleocharis is unusually difficult because relatively few macroscopic characters are provided by the simple structure characteristic of the genus (only two leaves, basal, without blades or with only rudimentary blades, and unbranched aerial stems, each with a single terminal spikelet and without an involucral bract). Undoubtedly much evolutionary convergence has occurred in most vegetative and reproductive structures (M. S. González-E. and J. A. Tena-F. 2000; E. H. Roalson and E. A. Friar 2000).

North American Eleocharis includes some extremely difficult species complexes that need taxonomic revision: (1) The E. palustris complex (species 17) is discussed under 1. E. palustris. (2) The E. tenuis complex (species 1621) is discussed under 21. E. tenuis. (3) The four species (species 5760) of 8c. Eleocharis subg. Zinserlingia that occur in North America belong to the E. quinqueflora (= E. pauciflora) complex, discussed under subg. Zinserlingia. (4) All six species of 8a2b. E. ser. Ovatae (species 4247) constitute a complex discussed under ser. Ovatae.

The supraspecific classification of Eleocharis used here is that of M. S. González-E. and P. M. Peterson (1997), which was based on a study of most species worldwide. Other recent classifications are based on more or less regional studies (H. K. Svenson 1957; T. V. Egorova 1981; I. Kukkonen 1990). A study using limited DNA data from 30 species (E. H. Roalson and E. A. Friar 2000), mostly from North America, indicates that the following supraspecific taxa are probably monophyletic: 8a2a. ser. Maculosae, 8a2b. ser. Ovatae, and 8d. subg. Limnochloa, whereas the following taxa are probably para- or polyphyletic: 8a1. sect. Eleocharis, 8a1a. ser. Eleocharis, 8a1d. ser. Tenuissimae, and 8a2. sect. Eleogenus.

Users of this treatment should be aware of the following: culms that are smooth when fresh are often ridged when dry; culms of pressed specimens are often flattened and must be carefully rehydrated and sectioned to determine the original cross-section shape ; culm widths given here are usually for culms pressed flat; floral scale widths are measured on flattened scales or by doubling the width measured on scales folded along the midrib ; and achene length does not include the tubercle, which is often included in descriptions published elsewhere. In this treatment, I describe the tubercle (style base) after the achene in consecutive sentences to stress the separate nature of the two structures.

Some species, mostly of 8a1d. Eleocharis ser. Tenuissimae, often proliferate from spikelets, often on arching or horizontal culms, especially when growing as submerged or floating aquatics. Because many such plants reproduce entirely asexually and have no normal spikelets or achenes, it is often impossible to identify them to species. The invalid name E. prolifera Torrey has sometimes been used for these plants. Species of ser. Tenuissimae in which the spikelets may be proliferous and which are easily confused with each other are E. baldwinii, E. brittonii, E. microcarpa, E. nana, E. retroflexa, and E. vivipara. Aquatic forms of at least some of those species are very hard to distinguish from Websteria confervoides (Poiret) S. S. Hooper. Other species in which the spikelets often poliferate or the culm tips root are E. pachycarpa of ser. Tenuissimae, E. melanocarpa of 8a1b. ser. Melanocarpae, and E. rostellata of 8a1c. ser. Rostellatae. When submersed , plants of E. acicularis of 8b. subg. Scirpidium and E. elongata and E. robbinsii of 8d. subg. Limnochloa may be entirely vegetative, the latter two species sometimes forming whorls of flaccid stems without spikelets.[2]

Physical Description

Species Eleocharis torticulmis

Plants perennial ; rhizomes 1.5–2 mm thick, scales persistent , 7–9 mm, thinly papery , sometimes fibrous ; resting buds unknown; caudices present, hard, 3 mm thick. Culms erect , markedly spirally twisted, markedly obliquely contracted near spikelet , when dry often with to 6 broad, rounded ridges on each side, greatly compressed , 3–4 times as wide as thick, 20–40 cm × 1.5–2.5 mm, firm; culm tufts not proximally bulbous. Leaves: distal leaf sheaths stramineous to medium (or dark) brown, papery, apex often dark brown to reddish, broadly obtuse . Spikelets 6–8 × 2–3 mm; proximal scale empty, 3–4 mm, shorter than to equaling spikelet; floral scales 8–10 per spikelet, 3.5–5 × 2 mm. Perianth bristles 0–5, unequal, rudimentary to equaling achene, the shorter stout, smooth or nearly so, the longer slender, densely spinulose . Anthers 1.8 –3 mm. Achenes stramineous to medium brown, thickly trigonous , 1.75–2.75 × 1–1.25 mm; beak 0.3–0.6 mm. Tubercles 0.25–0.6 × 0.3–0.55 mm. [source]


Flowers: Bloom Period: May, June, July.


Fruiting summer (Jun–Jul). Fens , wet meadows, vernal ponds ; of conservation concern; 1100 m [3].


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Name Status: Accepted Name .

Last scrutiny: 21-Jun-2005

Similar Species

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Members of the genus Eleocharis

ZipcodeZoo has pages for 107 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them:

E. acicularis (Least Spike-Rush) · E. acicularis f. occidentalis (Needle Spike-Rush) · E. acicularis var. acicularis (Needle Spike-Rush) · E. acicularis var. gracilescens (Needle Spikerush) · E. acicularis var. porcata (Needle Spikerush) · E. acicularis var. submersa (Needle Spikerush) · E. acuta (Common Spike-Rush) · E. acutangula (Acute Spikerush) · E. acutisquamata (Sharp-Scale Spikerush) · E. aestuum (Tidal Spikerush) · E. albida (White Spikerush) · E. ambigens (Obscure Spikerush) · E. atropurpurea (Purple Spikerush) · E. austrotexana (Rio Grande Spikerush) · E. baldwinii (Baldwin's Spikerush) · E. bella (Beautiful Spikerush) · E. bolanderi (Bolander's Spikerush) · E. brachycarpa (Short-Fruited Spikerush) · E. brittonii (Britton's Spikerush) · E. cancellata (Arizona Spike-Rush) · E. cellulosa (Carolina Spike-Rush) · E. coloradoensis (Little Headed Spikerush) · E. compressa (Flat-Stem Spike-Rush) · E. compressa var. acutisquamata (Sharpscale Spikerush) · E. congesta (Spikerush) · E. cylindrica (Cylinder Spike-Rush) · E. decumbens (Decumbent Spikerush) · E. diandra (Wright's Spikerush) · E. dulcis (Chinese Waterchestnut) · E. dulcis var. tuberosa (Chinese Water-Chestnut) · E. dulcis var. Variegata (Chinese Water Chestnut) · E. elegans (Elegant Spikerush) · E. elliptica (Elliptic Spikerush) · E. elongata (Slim Spike-Rush) · E. engelmannii (Engelmann Spike-Rush) · E. equisetoides (Horsetail Spikerush) · E. erythropoda (Bald Spike-Rush) · E. fallax (Creeping Spikerush) · E. fistulosa (Acute Spikerush) · E. flavescens (Pale Spikerush) · E. flavescens var. flavescens (Leafy Fleabane) · E. flavescens var. thermalis (Yellow Spikerush) · E. geniculata (Canada Spikesedge) · E. gracilis (Slender Spike Sedge) · E. halophila (Salt-Marsh Spike-Rush) · E. intermedia (Matted Spikerush) · E. interstincta (Knotted Spikerush) · E. kamtschatica (Kamchatka Spike-Rush) · E. kuroguwai (Spikerush) · E. lanceolata (Daggerleaf Spikerush) · E. macounii (Macoun's Spikerush) · E. macrostachya (Long Headed Spikerush) · E. mamillata (Soft Stemmed Spikerush) · E. mamillata mamillata (Soft Stemmed Spikerush) · E. melanocarpa (Black-Fruited Spike-Rush) · E. microcarpa (Small-Fruited Spike-Rush) · E. minima (Small Spikerush) · E. montana (Dombey's Spike-Rush) · E. montevidensis (Hairgrass) · E. multicaulis (Many Stalked Spike Rush) · E. mutata (Angled Spikerush) · E. nana (Hair-Like Spikerush) · E. nigrescens (Black Spikerush) · E. nitida (Quill Spikerush) · E. obtusa (Blunt Spikerush) · E. occulata (Limestone Spikerush) · E. ochrostachys (Spikerush) · E. oligantha (Fewflowered Spikerush) · E. olivacea (Bright Green Spikerush) · E. olivacea Torr. var. olivacea Torr. (Bright Green Spikerush) · E. olivacea var. olivacea (Bright Green Spikerush) · E. olivacea var. reductiseta (Bright Green Spikerush) · E. ovata (Ovate Spikerush) · E. pachycarpa (Black Sand Spikerush) · E. pachystyla (False Junco) · E. palmeri (Palmer's Spikerush) · E. palustris (Common Spike-Rush) · E. palustris palustris (Common Spikerush) · E. palustris uniglumis (Common Spikerush) · E. palustris var. calva (Creeping Spike-Rush) · E. parishii (Parish Spikerush) · E. parvula (Dwarf Spikerush) · E. quadrangulata (Square Stemmed Spike Rush) · E. quinqueflora (Few-Flower Spike-Rush) · E. radicans (Rooted Spike-Rush) · E. retroflexa (Coastal Plain Spikerush) · E. retroflexa chaetaria (Coastal Plain Spikerush) · E. reverchonii (Reverchon's Spikerush) · E. robbinsii (Robbins Spikerush) · E. rostellata (Beaked Spike-Rush) · E. schaffneri (Schaffner's Spikerush) · E. setifolia (Smallflower Spikerush) · E. sintenisii (Sintenis' Spikerush) · E. sphacelata (Bamboo Spike Sedge) · E. suksdorfiana (Suksdorf's Spikerush) · E. tenuis (Slender Spikerush) · E. tenuis (Willd.) J.A.Schultes var. tenuis (Willd.) J.A.Schultes (Slender Spikerush) · E. tenuis var. pseudoptera (Slender Spikerush) · E. tenuis var. tenuis (Slender Spikerush) · E. tenuis var. verrucosa (Slender Spikerush)

More Info

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Further Reading

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Data Sources

Accessed through GBIF Data Portal February 29, 2008:



  1. Peter W. Ball, A. A. Reznicek, David F. Murray "Cyperaceae". in Flora of North America Vol. 23 Page 3, 4, 192, 243, 252. Oxford University Press. Online at [back]
  2. S. Galen Smith, Jeremy J. Bruhl, M. Socorro González-Elizondo & Francis J. Menapace "Eleocharis". in Flora of North America Vol. 23 Page 4, 6, 7, 29, 60, 61, 121. Oxford University Press. Online at [back]
  3. "Eleocharis". in Flora of North America Vol. 23 Page 112, 113, 115. Oxford University Press. Online at [back]
Last Revised: 2015-01-30