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.
Author: The Morton Arboretum
From Flora of Indiana (1940) by Charles C. Deam
This variety grows in very sandy soil and is found mostly on sand ridges and dunes, in sandy fallow fields, and in the moist intervening sandy areas between sand ridges and dunes. In its habitat it is usually frequent, elsewhere it is absent.