Plants loosely cespitose; rhizomes horizontally spreading, reddish brown to dark brown, (10-)40-100 mm, slender. Culms 10-45 cm, smooth to weakly scabrous distally; bases (remnants of old leaves) slightly fibrous. Leaf blades green, 0.5-3.6 mm wide, herbaceous, papillose to scabrous abaxially, papillose to scabrous adaxially, blades of distal cauline leaves well developed. Inflorescences usually with both staminate and pistillate spikes; peduncles of staminate spikes 0.1-7.5 mm; proximal cauline bracts leaflike, usually shorter than inflorescences. Spikes: proximal pistillate spikes 1-3(-4) (basal spikes 0, rarely 1); cauline spikes overlapping or separated, with (3-)4-13 perigynia; staminate spikes 8-24 × 1.3-4 mm. Scales: pistillate scales dark reddish brown, with narrow white margins, ovate, 2-4 × 1.3-2.8 mm, equaling perigynium body, apex obtuse or acute to acuminate; staminate scales elliptic to ovate, 2.9-5.3 × 1.1-1.9 mm, apex obtuse or acute to acuminate. Anthers 1.8-4 mm. Perigynia pale green, veinless, obovoid, 2.2-3.4 × 1.1-1.5(-1.7) mm; beak straight, pale green, 0.5-0.9 mm, weakly ciliate-serrulate, apical teeth 0.1-0.4 mm. Stigmas 3. Achenes dark brown, obovoid, obtusely trigonous in cross section, 1.3-2.3 × 0.9-1.4(-1.6) mm. 2n = 36.