Mackenzie, Bull. Torrey Bot. Club. 43: 612. 1917 (as sub-bracteata).
Plants densely cespitose. Culms often lax, supported by other vegetation, 27—105 cm. Leaves: sheaths white-hyaline or green-veined with central white-hyaline strip, summits U-shaped to rounded, sometimes prolonged beyond collar; distal ligules 1.5—5.5 mm; blades 3—6 per fertile culm, 12—65 cm × 1.3—3.7(—4.6) mm. Inflorescences dense to open, green and brown, gold and brown, or brown, 1.3—3.5 cm × 7—23 mm; proximal internode 2—3(—4.5) mm; 2d internode 1—3 mm; proximal bracts bristlelike or rarely leaflike, longer than inflorescences. Spikes 4—11, densely aggregated, at least proximal 1—3 distinct, ovoid to broadly ovoid, 6—12.3 × 3.8—9.1 mm; base rounded; apex acute to rounded. Pistillate scales brown, red-brown, or coppery, with whitish, green, or pale brown midstripe, ovate, (3.2—)3.5—4.5 mm, shorter, narrower than, or covering perigynia, margin often indistinct, white, 0—0.4 mm wide, apex ± obtuse or rarely short-awned. Perigynia ascending to spreading, straw colored or gold to coppery, conspicuously (0—)5—9-veined abaxially, conspicuously 0—6-veined adaxially, veins not reaching top of achene, ovate to broadly ovate, plano-convex to biconvex, (2.9—)3.5—4.7(—5.7) × 1.2—1.7(—2.2) mm, 0.5—0.75 mm thick, ± leathery, margin flat, including wing 0.2—0.4 mm wide, ciliate-serrulate at least on distal body, with metallic sheen; beak often brown to dark brown at tip or white-hyaline, cylindric, unwinged, abaxial suture inconspicuous, distance from beak tip to achene 1.5—2.2(—2.6) mm, ± entire for (0.3—) 0.4—0.8 mm. Achenes broadly ovate to quadrate, 1.3—2.1 × 1—1.5(—1.7) mm, 0.5—0.6 mm thick.
Fruiting spring—summer. Meadows, swales, moist places, roadsides, along the coast and in Coast Ranges; 0—900 m; Calif.
Carex subbracteatais very similar to and perhaps conspecific with C. gracilior (R. Whitkus 1988).