Plants cespitose; rhizomes appearing elongate in old clumps. Culms 25–80 cm; vegetative culms few, inconspicuous, usually fewer than 15 leaves, not strikingly 3-ranked. Leaves: sheaths conspicuously green-veined nearly to collar, narrow hyaline band or sharp Y-shaped region at collar, adaxially firm, summits U-shaped, sheaths sometimes finely papillose; distal ligules 2.4–5.6 mm; blades 2–5 per fertile culm, 10–25 cm × 2–5 mm. Inflorescences dense to open, green or brown, 1.5–4 cm × 10–20 mm; proximal internode 2–12 mm; 2d internode 3–10 mm; proximal bracts scalelike, with bristle tips shorter than inflorescences. Spikes 3–6, distant, distinct, ellipsoid to ovoid-globose, 8–20 × 6–10 mm, base rounded or short-acute, apex broadly obtuse to rounded. Pistillate scales white-hyaline or brown with pale brown or green 1-veined midstripe, lanceolate, 3.3–4 mm, as long as and narrower than perignyia, apex acute or obtuse. Perigynia 15–80 in larger spikes, spreading, light to dark brown, inconspicuously or shortly veined on each face, broadly elliptic or orbiculate to sharply obovate, flat except over achene, 4–6.1 × 3–4.4 mm, 0.45–0.6 mm thick, sometimes nearly leathery, base rounded, margin flat, including wing 0.7–1.5 mm wide, smooth; beak spreading, light brown at tip, flat, 0.7–1.6(–1.8) mm, 1/3 length of body, ciliate-serrulate, abaxial suture with hyaline, pale brown margin, distance from beak tip to achene 2–3 mm. Achenes oblong, 1.5–2 × 0.9–1.2 mm, 0.3–0.5 mm thick. n = 33+III. 2n = 68, 70.

Fruiting early summer. Sandy, calcareous soils of marsh borders, bottomlands, ditches, thickets, and seasonally wet fields; 0–20 m; Fla.

Carex vexans is very similar to C. alata. However, even in their zone of potential overlap in northern Florida, the two species can be readily separated on the basis of pistillate scales, perigynium shape, and habitat (P. E. Rothrock et al. 1997).

See note under 146. Carex longii.