Herbs, perennial, cespitose, 50--150 cm. Stems compact. Leaves ascending in narrow fans, (19--)30--50(--60) cm; sheaths pinkish or pale red, soft, smooth; blade pale green proximally, distally deep lustrous green, linear, flattened, plane, 5--15 mm wide, margins smooth. Inflorescences: scape sheaths exceeded by leaves; scapes linear, straight, distally slightly compressed, 1--2 mm wide, smooth, 2-ribbed; spikes ovoid to ellipsoid or cylindric, 10--20(--25) mm, apex usually blunt; fertile bracts 5--8 mm, margins entire, apex rounded. Flowers: lateral sepals slightly to conspicuously exserted, slightly curved, 6--8 mm, keel scarious, apex not red, broad, thin, lacerate; petals unfolding in afternoon, blade obovate, 5--6 mm; staminodes bearded. Seeds translucent, narrowly ellipsoid to ovoid, (0.6--)0.7(--0.8 mm), irregularly ridged and cross-ridged. 2n = 18. Flowering summer--fall. Sandy or peaty shallows and shores of ponds and sluggish acidic streams; 0--100 m; Ala., Conn., Del., Fla., Ga., La., Maine, Md., Mass., Miss., N.H., N.J., N.Y., N.C., R.I., S.C., Tex.; West Indies (Cuba); Mexico (Tabasco); West Indies (Cuba); Central America (Belize, Honduras, Nicaragua). Although no specimens were seen for Virginia, Xyris smalliana is to be expected there.
Lvs linear, mostly (20-)30-50(-60) cm נ5-15 mm, deep lustrous green, flat or nearly so, usually anthocyanic at the dilated, thin, soft, keeled base; scapes 5-15 dm, smooth, terete and with very low ridges below, 1-2-ridged and somewhat flattened distally; spikes 1-2(-2.5) cm at maturity, ellipsoid or narrowly ovoid; lateral sep ±exserted distally, the keel broad, thin, lacerate toward the tip; pet-blades yellow, obovate, 5-6 mm, unfolding in the afternoon; 2n=18. Wet low ground, especially near the coast; Me. to Fla. and Miss. Early summer-fall. (X. congdonii)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.