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.

Flowering late spring--summer. Moist to dry coniferous and mixed woods; 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.