Plants solitary or sometimes mat-forming, rhizomatous. Leaves basal; petiole rounded to flattened, 2-10 cm; blade spatulate to obovate, 0.8-8 cm, thin, base cuneate to slightly attenuate, margins serrate to dentate, eciliate or sparsely glandular-ciliate, surfaces abaxially glabrous, adaxially sparsely brown-hairy. Inflorescences usually 10-15-flowered, lax, cylindric thyrses, (red), (4-)7-30 cm, sparsely purple-tipped stipitate-glandular. Flowers: sepals reflexed, oblong to elliptic; petals white, each with 2 basal yellowish green spots, elliptic to round, clawed, 2-5.5 mm, longer than sepals; filaments club-shaped, (to 6 mm); pistils connate 1/2+ their lengths; ovary superior, (to 1/3 adnate to hypanthium). Capsules green to yellow, distal 1/2 purple, ± folliclelike, (basally connate). 2n = ca. 56, 58.

Flowering summer-early autumn. Wet, rocky meadows, mountain to alpine streamsides; 800-4000 m; Alta., B.C., N.W.T., Yukon; Alaska, Idaho, Mont., Wash.

Although they have nearly disjunct sets of populations, the subspecies of Micranthes lyallii are difficult to distinguish from each other. The more northern plants tend to be larger with wider leaves and often have been called Saxifragalyallii subsp. or var. hultenii. Apparent hybrids with M. odontoloma occur in Alberta, British Columbia, and northern Idaho, and near Glacier National Park, Montana.