Perennial herb with knotted, tuberous rhizomes, tufted 10 - 30 cm tall Leaves: alternate, light green, 5 - 20 cm long, 0.5 - 2.5 mm wide, flat, linear, parallel-veined, keeled beneath, with a sheathing base that encloses the stem. Inflorescence: consisting of one to a few terminal spikes, subtended by spirally arranged leafy bracts. Bracts two to four, more or less horizontal, unequal, 4 - 15 cm long, flat. Rays (branches of inflorescence) zero or one to three, 1 - 4 cm long. Spikes 8 - 16 mm long, densely egg-shaped, consisting of 20 to 60 spikelets. Flowers: minute, in the axil of a floral scale, lacking sepals and petals. Stamens exserted. Anthers about 0.5 mm long. Pistil one. Style about 1 mm long. Stigma 1 - 1.5 mm long. Fruit: a one-seeded achene, stalkless, dark brown to black, about 1.5 mm long, 0.5 - 1 mm wide, ellipsoid with a small, slender point at the rounded apex, three-angled, tiny-dotted. Seed with a thin, non-adherent wall. Culm: 10 - 30 cm long, about 0.5 mm wide, triangular in cross-section, solid. Spikelets: 3 - 7 mm long, 2.5 - 3.5 mm wide, compressed, narrowly lance-shaped with a rounded or tiny-pointed apex, subtended by two small bracts, with three to seven floral scales. Scales whitish to reddish brown, 2 - 2.5 mm long, about 1.5 mm wide, narrowly elliptic with a tiny-pointed apex, three- to five-ribbed, lowest one empty.
Similar species: No information at this time.
Flowering: June to late September
Habitat and ecology: Sandy soil.
Occurence in the Chicago region: native
Etymology: Cyperus is the ancient Greek word for sedge. Lupulinus means "resembling hops." Macilentus means lean or thin.