Plains Flat Sedge

Cyperus onerosus is apparently restricted to Andrews and Winkler counties in Texas.

This interesting endemic is most similar to Cyperus dentatus; it lacks tubers and apparently is not proliferous.

Herbs, perennial, cespitose, rhizomatous; base cormlike; rhizomes scaly, 12 cm × 2 mm. Culms trigonous, 20–55 cm × 1.2–11.8 mm, glabrous. Leaves V-shaped, 12–30 cm × 2–3 mm. Inflorescences: heads digitate, 12–20 mm diam.; rays 7–12, 1–13 cm; 2d order rays 1–3 cm (sometimes absent); bracts 3–5, longest ± erect, V-shaped, 5–12(–18) cm × 2–3 mm. Spikelets (8–)20–30, linear-lanceoloid, compressed, 5–10(–14) × 1.4–1.7 mm; floral scales (8–)16–26, laterally brown to reddish brown, medially green, laterally 1-ribbed, medially 3-ribbed, broadly elliptic, 2–2.5 × 1.2–1.6 mm, apex with slightly excurved cusp 0.2–0.3 mm. Flowers: stamens 3; anthers 1 mm, connective apex reddish, subulate, 0.1 mm; styles 1–1.5 mm; stigmas 1.5 mm. Achenes white to light brown, sessile, ellipsoid, 0.7–0.8 × 0.25–0.35 mm, apex obtuse, apiculate, surfaces puncticulate.

Tex.

Fruiting early summer (May–Jun).

Permanent pools and wet swales between sand dunes; of conservation concern; 1200m.

Cyperus onerosus is a species of sedge that is native to parts of Texas.

Cyperus onerosus adalah spesies tumbuhan yang tergolong ke dalam famili Cyperaceae. Spesies ini juga merupakan bagian dari ordo Poales. Spesies Cyperus onerosus sendiri merupakan bagian dari genus Cyperus. Nama ilmiah dari spesies ini pertama kali diterbitkan oleh M.C.Johnst..

Cyperus onerosus là loài thực vật có hoa trong họ Cói. Loài này được M.C.Johnst. mô tả khoa học đầu tiên năm 1964.