Cyperus lupulinus (Spreng.) Marcks

Perennial from short, tuberous-knotty rhizomes; stems 1–5 dm, smooth, rather obtusely angled, 0.4–1.2 mm thick; lvs light green, 1–3.5 mm wide, flat or folded, shorter than the stem; invol bracts 2–4, widely spreading to more often deflexed, the margins of these and the cauline lvs scabrous; infl usually a single subglobose or hemispheric sessile spike, or seldom with a few rays to 7 cm, each bearing a similar but smaller spike; spikelets drab-green or light reddish-brown, very crowded, radiating from the axis, flattened, 2.5–4 mm wide, (3–)6–22-fld; scales oblong-elliptic, 2–3.5 mm, in half-view from the side about a third as wide as long, multinerved, obtuse or with a minute mucro 0.1–0.4 mm, readily deciduous; rachilla-joints sharp-edged but not winged; anthers 0.3–0.6 mm; achene trigonous, with flat or only slightly concave sides, 1.4–2.2 mm, about half as wide, or a bit wider; 2n=ca 166. Dry woods and fields; abundant; Me. and s. Que. to Minn., S.D., and Colo., s. to Fla. and Tex. (C. bushii; C. macilentus; C. filiculmis var. m.)