Culms trigonous, scabrous-angled distally, (30-)40-120 cm; vegetative culms somewhat taller. Leaves: basal sheaths brown; sheaths glabrous, inner band green, veined, apex hyaline, prolonged 1-4.5 mm; ligules 2.2-8 mm; blades 2.5-4.6 mm wide. Inflorescences nearly cylindric, except near apex, 2.5-7(-9) cm; spikes ascending, ovate, 3.2-11 × 1.1-7 mm, basal spikes slightly more prominent than middle spikes. Pistillate scales pale brown to straw colored at maturity, hyaline margins, ovate, apex acute to acuminate, glabrous. Staminate scales pale brown to straw colored, narrowly ovate, apex acute, glabrous. Perigynia (2.5-)2.8-4.1(-4.6) × 1.3-2 mm; beak 0.4-1(-1.2) mm. Achenes brown.
Fruiting Jun-Jul. Fens, wet prairies, sedge meadows, marshes, wet, open thickets, open swamps, stream, pond, and lakeshores, ditches, often in shallow water; 0-2100 m; Alta., B.C., Man., N.W.T., Ont., Que., Sask.; Colo., Idaho, Ill., Ind., Iowa, Mich., Minn., Mo., Mont., Nebr., N.Y., N.Dak., Ohio, Pa., S.Dak., Wis., Wyo.
Carex sartwellii is an important wetland species in portions of the Midwest and West, but becomes increasingly uncommon and local eastward. It forms large, loose clones, but can be easily overlooked because flowering and fruiting are sometimes uncommon. Once seen, the tall, tristichous vegetative culms scattered along the rhizome are distinctive.
Stems 3-8 dm, scattered on long, coarse, dark rhizomes, strongly aphyllopodic, the lvs well distributed along the lower half of the stem, flat, 2-5 mm wide; sheaths elongate and firm, the ventral part tending to be partly greenish or greenish-striate; spikes numerous; 20+, sessile, inconspicuously bracteate (or the lowest one more evidently so), androgynous or some wholly staminate or wholly pistillate, the middle ones, especially, often staminate, ovoid, ca 1 cm or less, closely crowded into a ±cylindric to sometimes ovoid infl 2-5 cm (only the lowest ones somewhat separate); pistillate scales usually pale brown to stramineous; perigynia 2.3-4 mm, broadly lanceolate to round-ovate or ±elliptic, planoconvex, sharp-edged, tending to be serrulate distally, evidently several-nerved dorsally, usually less so ventrally, spongy at the base, ±abruptly contracted into the short (0.4-1 mm), minutely bidentate beak; achene lenticular; 2n=62. Wet meadows, open swamps, and shallow water; N.Y. and Ont. to B.C., s. to Ind., Mo., and Colo.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Occasional in marshes and marly sloughs, more rarely in sandy ditches, in the northern half of the state; becoming frequent in the dune area. [Variety stenorrhyncha, a form with perigynia 4-4.5 mm long and gradually tapered into the beak, is] known only from two localities, both in Lake County: in a prairie marsh south of Sheffield St. and west of Calumet Ave., two miles north of Hammond, Deam no. 53920 (Deam Herbarium); and on a prairie east of Wolf Lake, Hermann no. 6052 (Type in Gray Herbarium).