Swan sedge is a graminoid, 0.5-1m tall, with distant basal lateral spikes and pistillate terminal spike. At least half the flowers are female, staminate at the base. Perigynia are ascending, obscurely 5-13-veined, obovate-circular, trigonous in cross section, and densely pilose. Beak is absent. Leaf blades are pubescent and longer than the culm, ligules are longer than wide. Pistillate scales are ovate, apex is acute to acuminate, awn is as long as perigynia. Staminate scales are ovate, apex is obtuse or acuminate.