in W. Aiton and W. T. Aiton, Hortus Kew. 5: 222. 1813.
Plants erect, 10–35 cm. Leaves 3–4, along middle portion of stem, spiraled to alternate, ascending to spreading; blade narrowly elliptic to ovate-lanceolate or oblong, 5–11 × 1.3–3.5 cm. Flowers usually solitary (rarely 2 in forma biflorum P. M. Brown); sepals green with reddish brown markings; dorsal sepal broadly elliptic to ovate-lanceolate, 15–25 × 5–10 mm; lateral sepals distinct, 12–20 × 1.5–4 mm; petals somewhat spreading, same color as sepals, somewhat spirally twisted, linear- to linear-lanceolate, 11–24 × 1–2 mm; lip white with green apex, usually with extensive reddish reticulations often merging toward apex, adaxially swollen near middle, 10–16 mm, apex abruptly deflected downward, orifice basal, 7–12 mm; staminode suborbicular. 2n = 20.
Phenology: Flowering May–Jun.
Habitat: Dry to moist open coniferous and mixed forests, coniferous-forested fens, beach thickets
Elevation: mostly 0–400 m
Man., N.S., Ont., Que., Sask., Conn., Maine, Mass., Mich., Minn., N.H., N.Y., Vt., Wis.