Much like no. 22 [Carex muricata L.]; roots brown or blackish-brown; basal sheaths at first pale brown, becoming dark to blackish-brown; ligule short and blunt, usually wider than long; infl looser and more elongate, 3-10+ cm, the lowest spikes often 1-3 cm apart; perigynia appressed-ascending (or the lowest ones spreading), 3.5-4.5 mm, usually less than half as wide, ±equally narrowed to both ends, not corky; 2n=56, 58. Native of Europe, established in disturbed sites from Mass. to D.C. and Ont. (C. virens)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.