Plants 5-30 cm. Roots solitary, vertical, tuberous, turbinate, mostly to 1 cm diam. Leaves fugacious, 3-5, basal, spreading, oval-oblanceolate, 2-6 × 1-2 cm. Spikes loosely spiraled, 4-7 flowers per cycle of spiral; rachis glabrous. Flowers pure white, gaping from near middle, tubular portion less than 3 mm; sepals distinct to base, 5 × 1 mm; lateral sepals slightly spreading; petals linear to lance-oblong, 5 × 1 mm, apex acute to obtuse; lip 5 × 2.5 mm, ovate to oblong, apex dilated with broad crisped, finely lacerate margin; veins several, branches very short; basal calli long-pointed, mostly to 1 mm; viscidium linear-lanceolate; ovary mostly 3 mm. Seeds monoembryonic. Flowering Jun--Sep. Dry to open woods, outcrops, old fields, roadsides, cemeteries; 0--400 m; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Mass., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va. The nomenclatural history of Spiranthes tuberosa is rather complex, and among the names applied to it are Spiranthes beckii Lindley and Ibidium beckii (Lindley) House. See D. S. Correll (1950) for a discussion. This species is easily recognized by its pure white flowers, broad crisped lip, and fugacious leaves.
Slender, 1.5-3 dm; root single (unique among our spp.), turbinate, to 6(-10) cm, 4-12 mm thick, sometimes accompanied by the partly decomposed root of the previous year; basal lvs ephemeral, usually ovate, short-petiolate, 2-4(-5) cm, 6-15(-20) mm wide; usually 4-6 bladeless sheaths on the stem; infl 2-8+ cm, its rachis (as well as the whole herbage) glabrous, the ±cylindric fls rather closely set in a single long spiral, 3-5.5 mm, pure white, the lip broadly ovate, distally truncate or sometimes rounded and crisped or slightly erose, puberulent with minute hairs 0.2-0.4 mm on the upper surface, minutely papillate below, the basal callosities less than 1 mm. Acid, usually rather dry soil; Mass. to Fla., w. to Ill., Mo., and Tex. Aug., Sept. (S. grayi; S. beckii, misapplied)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.