Smooth Flatsedge

Western desert (Qattara).

Perennial.

Cyperus laevigatus is one of only two species of subg. Juncellus in the New World. It can be distinguished from all other New World species of Cyperus by its two stigmas and disclike, strongly flattened achene, which is borne with its face toward the rachilla. Species of subg. Pycreus, especially C. niger, have been misidentified as C. laevigatus, probably because of the dark, shiny spikelets. All species of subg. Pycreus have biconvex achenes like C. laevigatus; in species of subg. Pycreus the achene is attached with an edge toward the rachilla; in C. laevigatus the achene faces the rachilla.

Herbs, perennial, rhizomatous. Culms single or close together, trigonous to ± terete, (1–)8–30(–60) cm × (0.3–)0.6–1.5(–2.2) mm, glabrous. Leaves: blades present or reduced to sheaths, base of culm covered with reddish sheath 5–25 mm, distally short toothed 1–2 mm, or leaf blades involute, 1–7 cm × 0.3–1(–1.6) mm. Inflorescences: heads appearing lateral, spikes ± digitate, 5–15 × 5–15 mm; rays absent, sometimes 1, to 2 mm; bracts (1–)2(–3), longer bracts erect, appearing as continuation of culm, shorter bract(s) horizontal or ascending, longer bracts (1–)2–8(–12) cm × 0.5–3 mm, shorter (0.3–)1–4.5 cm × 0.2–1 mm. Spikelets (1–)2–7(–14), whitish green to reddish, compressed-turgid, ellipsoid to oblong-lanceoloid, 4–7(–12) × (1.6–)2–3(–3.6) mm; floral scales (8–)12–22, off-white, whitish with red speckles, or with single red spot 0.5 mm wide, medially whitish, oblong-laterally ribless or weakly 2-ribbed, medially weakly 1–3-ribbed, obovate to orbiculate, 1.5–2 × (1.3–)1.6–2 mm. Flowers: anthers (0.5–)0.7–1 mm, connective apex reddish, 0.1–0.2 mm; styles 0.8–1.2 mm; stigmas 0.7–1 mm. Achenes gray, glossy, oblong-ellipsoid to ovoid, (1.2–)1.3–1.5(–1.8) × (0.7–)0.8–1(–1.2) mm, base cuneate to stipelike, apex apiculate, surfaces finely reticulate to papillate.

Perennial, (5-)20-65 cm, forming small tufts or stems in rows. Rhizome horizontal, creeping, (1-)1.5-3 mm diam., covered with dark brown or reddish scales. Stem 0.5-5 mm diam., terete or obtusely trigonous, yellow green or grey green, smooth. Leaves mostly much reduced; sheaths up to 20 cm, brown to dark brown, sometimes reddish, mouth margin concave; ligule 0; blade up to 10 or reduced to a point. Inflorescence capitate, pseudolateral, 7-25 mm, one cluster of (1-)3-10(-more than 30) spikes; bract usually one, as a continuation of stem, 5-50 mm, subterete, obtuse (sometimes another short, second bract can be distinguished); spikes 6-20 x (1.5-)2-3.5 mm, often curved, turgid, with 10-40 closely imbricate glumes, glume-like bract, c. 2 mm, glume-like prophyll c. 2 mm; rachis 4-angled, concave side 1-1.2 mm wide, convex side 0.5-0.8 mm wide, internodes 0.7-1 mm, winged; glumes 1.8-3 mm, membranaceous, widely cymbiform, obtuse or mucronate, mid-nerve at apex slightly keeled, from yellowish or grey to dark reddish brown, glossy, margins narrowly scarious. Flowers on concave side of rachis. Nut 1.3-1.7 x c. 1 mm, ellipsoid or obovoid, grey-brown to black-brown, adaxial side flat, pressed against the rachis, abaxial side rounded, glossy, smooth or more or less clearly reticulate.

Ariz., Calif., N.C., Tex.; Mexico; West Indies; South America; Europe; Asia; Africa.

Distribution: From C. Asia, Idia and Pakistan W to southern N. America ans S. America.

Fl. Per.: Practically all year round.

Fruiting summer.

Alkaline grasslands, hotsprings, ditches, brackish marshes; 0–1000m.

In coastal salt marshes, beach depressions, shores of lakes, streams, irrigation channels, saline depressions.

Acorellus laevigatus (Linnaeus) Palla; Chlorocyperus laevigatus (Linnaeus) Palla; Juncellus laevigatus (Linnaeus) C. B. Clarke; Pycreus laevigatus (Linnaeus) Nees

Juncellus laevigatus (L.) C.B.Clarke in Hook.f., Fl. Brit. Ind. 6: 596. 1893. Acorellus laevigatus (L.) Palla in W.D.J. Koch, Syn. deut. schweiz. Fl. ed.3, 2: 2558. 1905; Rottboell, Descr. et Iconum: Tab. 16, fig.1. 1773. Rateeb & Sherif, Fl. Libya 120: fig. 5. 1985. N. Feinbrun-Dothan, Fl. Palaestina 4: pl. 480. 1986.

laevigatus: smooth

Starr 050128-3310 Cyperus laevigatus

Cyperus laevigatus is a species of sedge known by the common name smooth flatsedge.