Plants colonial, long-rhizomatous. Culms (10-)20-85 cm. Leaves 2-8.5 mm wide, sparingly scabrous. Spikes 4-6, erect; lateral spikes pistillate with a few staminate flowers proximally and rarely also distally, narrowly elliptic, 11-4.5 × 5.5-11 mm; terminal spike staminate, sometimes gynecandrous or abortive, 9-42 × 1.5-3.5 mm. Pistillate scales with distinct body, 2.9-7(-11.8) × 0.4-0.9(-1.1) mm, body 1.5-2.5 mm, translucent, apex with long, scabrous awn to 1.4-4.5(-9) mm, exceeding perigynia. Staminate scales ± tightly imbricate, lanceolate, narrowly ovate, or oblong-obovate, 3.3-9.3(-12.5) × 0.9-1.6 mm, apex acute to truncate-erose or retuse, sometimes with scabrous awn to 0.1-6.2(-9.2) mm. Perigynia horizontal, 3.2-5.1(-5.6) × 1.3-2.5 mm, minutely pustulate; beak 1.2-2.1 mm, smooth. Achenes trigonous-obovoid, sides strongly concave, 1.2-1.8(-2.1) × 0.9-1.3(-1.5) mm, less than 2 times as long as wide; style deciduous, straight or sinuous.
Fruiting summer. Wet meadows and woods, muddy margins of lakes and ponds, roadside ditches; 0-500 m; Ala., Ark., Fl., Ga., Ill., Kans., Ky., La., Miss., Mo., Nebr., N.Mex., N.C., Okla., S.C., Tenn., Tex., Va.; Mexico (Coahuila, Nuevo León); South America.
Carex aureolensis is similar to C. frankii and only recently has been recognized as a distinct species based on its staminate and pistillate scale morphology, growth habit, and distribution.