Cyperus polystachyos Rottbøll var. macrostachyos Boeckeler

Herbs, annual, cespitose. Culms trigonous, 5–50 cm × 0.4–2 mm, glabrous. Leaves flat, 10–30 cm × 1–3 mm. Inflorescences: heads loosely globose, 10–22 mm diam.; rays 0–6, 1–7 cm; bracts 3–6, horizontal to slightly ascending, flat, 3–26 cm × 1–3 mm. Spikelets 6–20, linear-lanceoloid, compressed, 7–30 × 2–3 mm; floral scales 8–28, stramineous to light reddish brown, laterally ribless, ovate, 2.7–3.6 × 1.6–1.8 mm. Flowers: stamens 2; anthers 0.5 mm, connective apex reddish, subulate, 0.1–0.2 mm; styles 1.9–2.1 mm; stigmas 1–1.3 mm. Achenes brown, oblong, 1.2–1.6 × 0.6–0.9 mm, base cuneate to ± stipelike, apex obtuse, apiculate, surfaces minutely punctate.

Fruiting summer. Swales between dunes, upper edges of tidal marshes, occasionally emergent shorelines, roadsides, inland ditches; 0(–50) m; Conn., Ga., Ill., La., Maine, Mass., N.H., N.J., N.Y., N.C., R.I., S.C., Va.