Culms round or trigonous, filiform, wiry, angles proximal to spike blunt or sharp, 5–35 cm, shorter than or longer than leaves. Leaves: basal leaf sheaths fibrillose when old; blades yellow-green or bright green, involute-cylindric, quill-shaped, 6–25 cm, 0.3–0.7 mm wide near base. Spike 7–30 × 3–7 mm, staminate portion 4–14 mm. Proximal pistillate scales pale red-brown with white or gold margins, broadly obovate, 2.3–4.5(–6.5) × 1.7–4 mm, shorter or longer than perigynia, apex obtuse to short-awned. Staminate scales red-brown with broad, white margins, broadly obovate, apex obtuse. Perigynia (2–)5–18, appressed to ascending, white to gold, obovate to orbiculate, 1.9–4.8 × 1.3–2 mm, body conspicuously hirsute or pubescent, at least distal 1/4 (occasionally only proximal to beak); beak 0–0.8 mm, style base often conspicuously exserted from beak; rachilla present. Achenes obovate to elliptic, 1.5–3.3 × 1.1–1.9 mm. Stigmas ± black.

Varieties 2 (2 in the flora): North America.

Lower Taxa

• Carex filifolia var. erostrata Kükenthal
• Carex filifolia var. filifolia