Buttonbush Flatsedge

The combination of spreading floral scales and scabrid culms separates this rather uncommon species from any others occurring in its range. The scarcity of Cyperus cephalanthus in the United States and its disjunct distribution suggest it might be naturalized rather than native. It was collected early in the nineteenth century in Louisiana, and the amphitropical distribution is not without parallel in the genus (cf. 12. C. eragrostis).

Cyperus cephalanthus has been treated as a variety of the widespread, polymorphic South American C. laetus (G. Kükenthal 1935–1936). Recognition of C. cephalanthus as a species follows recent American floristic practice.

Herbs, perennial, rhizomatous. Culms trigonous, 40–70(–100) cm × 2–3 mm, scabrid or hirtellate, either immediately proximal to apex or over distal 1/2 of culm. Leaves flat, 30–80 cm × 4–10 mm, scabrid on margins, ribs on abaxial surface. Inflorescences: spikes ovoid, 12–20 × 13–18 mm; rays 3–6, 4–10(–16) cm, glabrous; bracts 3–5, ± horizontal to reflexed, 3–12(–36) cm × 0.4–3(–5) mm, scabrid like leaves; rachilla deciduous, essentially wingless or wings inconspicuous, hyaline, 0.1(–0.2) mm wide. Spikelets 25–50(–80), oblong, quadrangular-compressed, 5–10 × 2.5–3.5 mm; floral scales deciduous, 4–10(–14), marginally clear, laterally brownish to clear distally, or light brown or reddish brown, blunt, laterally 3(–4)-ribbed, ovate-lanceolate, 2.5–3 × (1.2–)1.4–2 mm, often erose apically, apex acute to obtuse, entire or emarginate. Flowers: anthers 0.4–0.6 mm; styles 0.8–1.2 mm; stigmas 2 mm. Achenes brown to reddish brown, ± stipitate, ellipsoid, 1.2 × 0.5–0.6 mm, apex obtuse, scarcely to distinctly apiculate, surfaces puncticulate.

La., Okla., Tex.; South America (Argentina, Brazil, Paraguay, Uruguay).

Fruiting summer.

Wet prairies; 0–50m.

Cyperus laetus J. Presl & C. Presl var. cephalanthus (Torrey & Hooker) Kükenthal

Cyperus cephalanthus, commonly known as the buttonbush flatsedge, is a species of sedge that is native to southern parts of North America and South America.

Cyperus cephalanthus adalah spesies tumbuhan yang tergolong ke dalam famili Cyperaceae. Spesies ini juga merupakan bagian dari ordo Poales. Spesies Cyperus cephalanthus sendiri merupakan bagian dari genus Cyperus. Nama ilmiah dari spesies ini pertama kali diterbitkan oleh Torr. & Hook..

Cyperus cephalanthus là một loài thực vật có hoa trong họ Cói. Loài này được Torr. & Hook. mô tả khoa học đầu tiên năm 1836.