Culms 7-31 cm. Leaf blades involute, bristlelike, 3-21 cm × 0.2-1 mm. Inflorescences: proximal bract sheaths 2.5-8 mm; pistillate spikes 3-7 × 1.5-6 mm; staminate spikes 3-10 × 0.5-1.5 mm, inconspicuous. Scales: pistillate scales white-hyaline, with green or brown midvein, ovate to ovate-circular, 1-2 × 0.7-1.4 mm, shorter than or equaling perigynia; staminate scales, white-hyaline, with broad hyaline margins, elliptic-oblanceolate, 2.6-4 × 0.7-2 mm, apex obtuse or subacute. Anthers 1.3-1.8 mm. Perigynia light green becoming dark brown and glossy, 1.5-2.2 × 0.7-1.1 mm; beak 0.2-0.4(-0.5) mm. Achenes ellipsoid-obovoid. Fruiting late spring-mid summer. Usually in conifer or mixed forests, occasionally fens, stable dunes and alvar, on neutral or calcareous substrates; 0-2000 m; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., Que., Sask., Yukon; Ala., Alaska, Ark., Conn., Ill., Ind., Iowa, Ky., Maine, Mass., Mich., Minn., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., S.C., S.Dak., Tenn., Vt., Va., W.Va., Wis.; c Mexico.
From Flora of Indiana (1940) by Charles C. Deam
Apparently restricted to the northwestern and southeastern corners of the state. In the north it is known only on the dunes in dry sandy thickets and in open situations. In southern Indiana it is found in wet crevices of limestone bluffs near the Ohio River. Care eburnea retains its fruit over a longer period than any of our other species due to the tendency of the perigynia to persist in the spikes long after maturity. Although the fruit ripens from May to July most of the plants have dropped relatively few of their perigynia, as a rule, by October and frequently the old prostrate culms from the preceding year will be found to have spikes in which many perigynia are still firmly attached.
Densely tufted and with long, slender rhizomes; stems very slender, 1-3 dm; lvs shorter than the stems, involute, 0.5 mm wide or less; spikes subtended by short bladeless sheaths, the pistillate 2 or 3, 3-6 mm, 2-6-fld, on long erect peduncles overtopping the terminal linear staminate spike; pistillate scales broadly ovate, much shorter than the perigynia, whitish with narrow green midvein, obtuse or acutish; perigynium-body light green, some becoming brown, 1.5-2 mm, obovoid, trigonous, ribbed on the lateral angles, finely few-nerved, glabrous, filled by the trigonous achene, abruptly narrowed to a conic beak 0.2 mm. Calcareous soil; Nf. to Mack. and B.C., s. to Va., Ala., Nebr., and Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.