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.