388. Carex hystericina Muhlenberg ex Willdenow, Sp. Pl. 4(1): 282. 1805.
Plants densely to loosely cespitose; rhizomes short, no more than 10 cm. Culms trigonous in cross section, 20–100 cm, scabrous-angled distally. Leaves: basal sheaths usually strongly tinged with reddish purple; ligules longer than wide; blades pale to mid green, flat to W-shaped, 2.5–8.5 mm wide, glabrous. Inflorescences 2.5–12(–20) cm; proximal bract 4–30 cm, exceeding inflorescence; proximal (1–)2–3(–4) spikes pistillate, erect or often the proximal pendent; terminal 1 spike staminate. Pistillate scales lanceolate, 2.3–6.5 × 0.5–1.1 mm, shorter than perigynia, margins ciliate, , apex truncate to retuse, scabrous-awned, awn longer than body. Staminate scales scabrous-awned, sometimes also ciliate-margined. Perigynia spreading or the proximal reflexed, strongly 13–21-veined, veins mostly separated by 3+ times their width, confluent at or proximal to mid beak (except for 2 prominent lateral), elliptic, 4.5–7.3 × 1.4–2.1 mm, herbaceous, apex contracted; beak 1.9–2.8 mm, smooth, bidentulate, teeth straight, 0.3–0.9 mm. Stigmas 3. Achenes pale brown, trigonous, smooth.
Fruiting May–Jul. Open swamps, sedge meadows, fens, stream, pond, and lakeshores, seeps, springheads, ditches, mostly in calcareous soils; 0–2000 m; B.C., Man., Nfld. and Labr., N.S., Ont., Que., Sask.; Ark., Conn., Ill., Ind., Iowa, Kan., Mass., Mich., Minn., Mo., Mont., Nebr., N.J., N.Mex., N.Y., Ohio, Pa., S.Dak., Tenn., Tex., Utah, Va., W.Va., Wis., Wyo.
Carex hystericina is widespread and common, even weedy, in regions with calcareous substrates. It hybridizes uncommonly with C. pseudocyperus and more rarely with C. comosa, C. schweinitzii, C. utriculata, and C. vesicaria. Hybrids are sterile and intermediate in morphology. The species epithet is often, but not originally, spelled “hystricina.”