Culms to 80 cm × 3-8 mm, scabrous. Leaves: sheath fronts not spotted, slightly thickened near hyaline margins, apex convex, membranous, rugose; ligule retuse or rounded, to 3 mm, free limb to 0.2 mm; blades 60 cm × 5 mm, shorter than flowering stem. Inflorescences spicate, 3-7 cm × 15-25 mm, with 10-15 branches, proximal branches not distinctly separate; the proximal internode to 10 mm; bracts setaceous, usually only the proximal conspicuous. Scales hyaline, pale brown, becoming colorless with green midrib, awn usually not longer than the body. Perigynia pale brown, body broadly ovate, 3.2-4 × 2-2.6 mm, base rounded or cordate, apex abruptly contracted to beak; beak 1.3-1.5 mm, 1/3 length of perigynium. Achenes brown, ovate, 1.5-1.9 × 1.2-1.6 mm, dull.
Carex fissa can be distinguished from other taxa in the section by the conspicuously larger perigynia. The two distjunct varieties appear to be consistently separable by the characteristics provided below and may warrant recognition as distinct species.