Loosely cespitose; stems slender but erect, 2–6 dm, ± strongly surpassing the lvs; main lvs 1–1.5 mm wide; infl longer or shorter than the lowest bract, 1–2 cm, with a small terminal staminate spike and 2 or 3 ± closely aggregated pistillate ones; pistillate scales reddish-brown with broad hyaline margins and pale center, wider but evidently shorter than the perigynia, blunt or rounded, sometimes shortly mucronate; perigynia 3–12, dull green or yellowish-green, short-hairy, 2.7–4.1 mm, slightly flattened, narrowly obovoid above a stipe-like base, 2-keeled, abruptly contracted into a slender beak 0.5 mm; achene rounded-trigonous; 2n=36. Open woods, ± calciphile; Que. to Yukon, s. to N.J., Mich., Minn., Nebr., and B.C. (C. nigromarginata var. elliptica; C. albicans, misapplied)