Herbs, perennial, cespitose, 30--70 cm, base bulbous in maturity. Stems compact. Leaves ascending, 15--45 cm; sheaths soft, base pink or red; blade deep green, linear, flattened, somewhat twisted, 5--10 mm wide, smooth, margins somewhat scabrous. Inflorescences: scape sheaths exceeded by leaves; scapes linear, terete, distally somewhat compressed, 1 mm wide, 2--5-ribbed, ribs papillate; spikes ellipsoid to broadly ovoid, 10--15 mm; fertile bracts (5.5--)6--6.5(--7) mm wide, margins entire, apex rounded. Flowers: lateral sepals included, slightly curved, (4.5--)5 mm wide, keel scarious, lacerate; petals unfolding midday, blade obovate, 4.5 mm; staminodes bearded. Seeds opaque, ellipsoid, 0.5-0.6 mm, finely and irregularly ridged. 2n = 18.

Flowering summer--fall. Fens and seeps over calcareous rock, streambanks in calcareous districts; of conservation concern; 0--250 m; Ala., Ga., Tenn.

Xyris tennesseensis is unusual in habitat since because its sites are usually basic and its associates are fen or basic soil plants.