Stems ± strongly thickened, base not bulbous. Inflorescences: racemes dense, 35–65 × 1.5–4 cm. Flowers 8–35, showy; perianth open; sepals reddish purple, sometimes yellowish near base, or completely yellow, lanceolate, 3-veined, 6–12 mm; dorsal sepal arching over column, nearly adhering to it; lateral sepals strongly spreading; petals arching over column, connivent with dorsal sepal, often yellowish basally, and streaked with purple, or completely yellow suffused with purple toward apex; lip red-purple, white, or white with purple streaks or spots, narrowly obovate, 4.8–9.5 × 2.5–5 mm, thin, usually with small (0.7 mm) tooth on each side, margins undulate-denticulate; column curved somewhat toward lip, yellow, often flushed with purple or white basally, and streaked or spotted with purple, 5–8.2 mm; ovary 5.9–10 mm; mentum prominent, protruding backward along ovary but free from it. Capsules ellipsoid, 10–25 × 6–9 mm. 2n = 40.
Phenology: Flowering late spring–summer.
Habitat: Moist to dry coniferous and mixed woods
Elevation: 0–2300 m
Alta., B.C., Alaska, Calif., Idaho, Mont., Oreg., Wash., Wyo.
In the Pacific Northwest Corallorhiza mertensiana is largely sympatric with C. maculata and occasionally intergrades with it. It frequently forms large clumps.