Plants loosely cespitose; rhizomes arching to ascending, dark reddish brown to purplish brown, 0-12 mm, slender or stout. Culms 7-47 cm, scabrous distally; bases strongly fibrous. Leaf blades bright green, usually shorter than stems, 1.4-4.5 mm wide, herbaceous, glabrous abaxially, strongly scabrous to papillose adaxially. Inflorescences usually with both staminate and pistillate spikes; peduncles of basal spikes arching, elongate, slender; peduncles of terminal staminate spikes 2-5 mm; proximal cauline bracts leaflike, usually shorter than (occasionally slightly exceeding) inflorescences. Spikes: proximal pistillate spikes 2-4 (basal spikes 1-2); cauline spikes overlapping or somewhat separated, with 3-10 perigynia; terminal staminate spikes 10-25 × 1.5-3.2 mm. Scales: pistillate scales purplish brown or reddish brown, with similarly colored or narrow white margins, ovate, 4.2-6.5 × 1.8-2.1 mm, equaling or exceeding perigynia, apex obtuse to cuspidate (awned in some basal spikes); staminate scales ovate to lanceolate, 4.2-7.6 × 1.8-2.1 mm, apex obtuse to acute or short-awned. Anthers 2-3.3 mm. Perigynia green, 12-20-veined conspicuous to at least mid body, globose to obovoid, (3.5-)3.8-5 × (1.6-)1.8-2.3 mm; beak straight, pale green, often tinged with dark reddish brown near apex, (0.5-)0.7-1.4 mm, ciliate-serrulate, apical teeth 0.2-0.3 mm. Stigmas 3. Achenes brown, globose to obovoid, round to obtusely trigonous in cross section, 1.9-2.7 × 1.6-2.3 mm.

Fruiting mid Apr-late Jun. Moist, shaded, acidic and serpentine slopes and stream banks in redwood, cypress, pine, and oak forests; 90-1500 m; Calif.