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Cyperus diandrus

(Umbrella Flat Sedge)


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Common Names

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Click on the language to view common names.

Common Names in English:

Umbrella Flat Sedge, low cyperus, low umbrella flatsedge, Umbrella Flatsedge

Common Names in French:

souchet diandre


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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 Cyperus

Herbs, perennial or less often annual , cespitose or not, rhizomatous , stoloniferous , rarely tuberous . Culms solitary or not, trigonous or round , glabrous or scabridulous with extrorse or antrorse (rarely retrorse ) prickles. Leaves usually basal; ligules absent; blades keeled abaxially, flat, V-, or inversely W-shaped in cross section . Inflorescences terminal , rarely pseudolateral, 1st order subumbellate to capitate, 2d order with spicate or digitately arranged spikelets , rarely a solitary spikelet; spikelets 1-150; 1st order rays unequal (rarely equal) in length , produced singly from the axils of inflorescence bracts ; involucral bracts 1-22, spirally arranged at culm apex, spreading to erect , leaflike. Spikelets: scales to 76, distichous, each subtending flower, cylindric to compressed , borne spicately or digitately at ends of rays (occasionally proliferous) . Flowers bisexual [rarely unisexual ], in axils of distichous floral scales, bases often decurrent onto rachilla as ± hyaline wings ; perianth absent; stamens 1-3; styles linear , 2-3-fid, base deciduous or persistent ; stigmas 2-3. Achenes biconvex , flattened, or trigonous.

Species ca. 600: pantemperate and tropical .[2]

Physical Description

Species Cyperus diandrus

Herbs, annual , cespitose, with fibrous roots . Culms trigonous , 4-25(-35) cm, glabrous . Leaves flat, 5-20 cm × 1.5-3 mm. Inflorescences: heads ± digitate, 12-22 mm diam.; rays 3-6, 1-6 cm; bracts 1-4, ± horizontal, flat, 1.5-15 cm × 1.5-3 mm. Spikelets 6-12, oblong-lanceoloid, compressed , 5-10 × 2.8-3.2 mm; floral scales 8-28, closely imbricate, stramineous to light brown or clear (marginal band bright red, spikelet thus appearing dark margined ), laterally ribless, oblong to ovate , 2.5-3 × 1.6-1.9 mm. Flowers: stamens 2(-3) ; anthers 0.3 mm, connective apex reddish, subulate , 0.1-0.2 mm; styles 0.3-0.5 mm; stigmas 2.2-3.1 mm. Achenes brown, network of ridges forming isodiametric or square cells , sessile or stipitate , obovoid to ovoid , 1-1.2 × 0.5-0.6 mm, stipe, if present, 0.1 mm, apex obtuse , apiculate , surfaces minutely punctate . Fruiting summer. [source]

Habit: Graminoid


Emergent shorelines , in sandy, peaty, or slightly brackish areas (though seldom where disturbed ); 0-600 m [3].

Typically found at an altitude of 0 to 995 meters (0 to 3,264 feet).[4]


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Duration: Annual


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Pycreus diander (Torr.) C. B. Clarke • Pycreus diander (Torrey) C. B. Clarke


Name Status: Accepted Name . Latest taxonomic scrutiny: 15-Mar-2000

Similar Species

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Members of the genus Cyperus

ZipcodeZoo has pages for 182 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them:

C. acuminatus (Short-Point Flatsedge) · C. aggregatus (Inflated Scale Flatsedge) · C. albostriatus (Dwarf Umbrella Grass) · C. alopecuroides (Foxtail Flatsedge) · C. alternifolia (Umbrella Plant) · C. alternifolius var. Gracilis (Dwarf Umbrella Plant) · C. amabilis (Foothill Flatsedge) · C. amuricus (Asian Flatsedge) · C. aromaticus (Navua Sedge) · C. articulatus (Jointed Flatsedge) · C. auriculatus (Eared Flatsedge) · C. bipartitus (Brook Flatsedge) · C. brevifolius (Mullumbimby Couch) · C. bulbosus (Australian Bush Onion) · C. calcicola (Caribbean Flatsedge) · C. cephalanthus (Buttonbush Flatsedge) · C. compressus (Poorland Flat Sedge) · C. confertus (West Indian Flatsedge) · C. congestus (Clustered Flatsedge) · C. corymbosus (Flat Sedge) · C. croceus (Baldwin's Cyperus) · C. cuspidatus (Coastal Plain Flatsedge) · C. cyperinus (Old World Flatsedge) · C. cyperoides (Pacific Island Flatsedge) · C. cyperoides pseudoflavus (Pacific Island Flatsedge) · C. deamii (Deam's Flatsedge) · C. dentatus (Toothed Flatsedge) · C. dentoniae (Hairy Flatsedge) · C. diandrus (Umbrella Flat Sedge) · C. difformis (Smallflower Umbrella Sedge) · C. diffusus (Dwarf Umbrella Grass) · C. digitatus (Finger Flatsegde) · C. dioicus (Flatsedge) · C. dipsaceus (Wright Flatsedge) · C. distans (Piedmont Flatsedge) · C. distinctus (Marshland Flatsedge) · C. echinatus (Globe Flatsedge) · C. elegans (Royal Flatsedge) · C. entrerianus (Deeprooted Sedge) · C. eragrostis (Drain Flat-Sedge) · C. erythrorhizos (Red-Root Flat Sedge) · C. esculentus (Yellow Nutsedge) · C. esculentus L. var. esculentus (Chufa Flatsedge) · C. esculentus var. esculentus (Chufa Flatsedge) · C. esculentus var. hermannii (Yellow Nutsedge) · C. esculentus var. leptostachyus (Yellow Nutsedge) · C. esculentus var. macrostachyus (Yellow Nutsedge) · C. esculentus var. sativus (Chufa) · C. exaltatus (Tall Flat-Sedge) · C. fauriei (Alpine Flatsedge) · C. fendlerianus (Fendler Flatsedge) · C. filicinus (Fern Flatsedge) · C. filiformis (Wiry Flatsedge) · C. flavescens (Pale Flatsedge) · C. flavicomus (White-Edge Flatsedge) · C. flexuosus (Vahl's Flatsedge) · C. floribundus (Rio Grande Sedge) · C. floridanus (Florida Flatsedge) · C. fugax (Withering Flatsedge) · C. fuligineus (Limestone Flatsedge) · C. fuscus (Brown Flatsedge) · C. giganteus (Giant Flatsedge) · C. glaber (Galingale) · C. gracilis (Slimjim Flatsedge) · C. granitophilus (Granite Flatsedge) · C. grayi (Gray's Flatsedge) · C. grayoides (Illinois Flatsedge) · C. haspan (Haspan Flatsedge) · C. hermaphroditus (Hermaphrodite Flatsedge) · C. hillebrandii (Hillebrand's Flatsedge) · C. hillebrandii var. decipiens (Hillebrand's Flatsedge) · C. hillebrandii var. hillebrandii (Hillebrand's Flatsedge) · C. houghtonii (Houghton's Flatsedge) · C. hyalinus (Queensland Sedge) · C. hypochlorus (Oahu Flatsedge) · C. hypochlorus var. brevior (Oahu Flatsedge) · C. hypochlorus var. hypochlorus (Oahu Flatsedge) · C. hypochlorus var. kauaiensis (Oahu Flatsedge) · C. hypopitys (Pinewoods Sedge) · C. hystricinus (Bristly Flatsedge) · C. imbricatus (Shingle Flatsegde) · C. involucratus (Galingale) · C. iria (Iria Flatsedge) · C. isocladus (Dwarf Papyrus) · C. javanicus (Javanese Flatsedge) · C. kunthianus (Maui Flatsedge) · C. kyllinga (Spikesedge) · C. laevigatus (Smooth Flatsedge) · C. lancastriensis (Many-Flowered Umbrella-Sedge) · C. lanceolatus (Epiphytic Flatsedge) · C. lecontei (Le Conte's Flatsedge) · C. lentiginosus (Latin American Flatsedge) · C. ligularis (Alabama Swamp Flatsedge) · C. longus (Sweet Cyperus) · C. louisianensis (Louisiana Flatsedge) · C. lucidus (Leafy Flat-Sedge) · C. lupulinus (Great Plains Flatsedge) · C. lupulinus lupulinus (Great Plains Flatsedge) · C. lupulinus macilentus (Great Plains Flatsedge) · C. lupulinus subsp. macilentus (Great Plains Flatsedge)

More Info

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Further Reading

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Data Sources

Accessed through GBIF Data Portal November 19, 2007:



  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. Gordon C. Tucker, Brian G. Marcks & J. Richard Carter "Cyperus". in Flora of North America Vol. 23 Page 7, 141, 154, 162, 163, 164, 168, 170, 184,. Oxford University Press. Online at [back]
  3. "Cyperus". in Flora of North America Vol. 23 Page 142, 157, 159, 161. Oxford University Press. Online at [back]
  4. Mean = 247.980 meters (813.583 feet), Standard Deviation = 182.790 based on 259 observations. Altitude information for each observation from British Oceanographic Data Centre. [back]
Last Revised: 2015-02-06