Shrubs much-branched and mat-forming, ca. 0.1 m. Twigs terete or slightly 2-angled proximal to node, glabrous or sparsely hairy. Leaves opposite; petiole absent or 0.1-2 mm, glabrous or puberulent; blade ovate or oval to narrowly lanceolate, 0.3-0.8 × 0.2-0.4 cm, margins revolute, apex obtuse, abaxial surface tomentulose, adaxial glabrous or sparsely puberulent toward base, midribs with stalked glands/purple clavate trichomes. Inflorescences terminal, corymbiform racemes or umbels, 2(-6)-flowered, sometimes flowers solitary. Pedicels 5-20 mm. Flowers: sepals crimson, ovate-lanceolate, 1.2-1.5 mm, apex obtuse, surfaces glabrous, margins ciliate; petals (spreading), connate ca. 1/2 their lengths, light to deep pink or white, 3-5 × 2-3.5 mm, glabrous; stamens 5; filaments 2-3 mm; style 0.5-0.8 mm. Capsules 2-3-locular, 3-4 × 3-4 mm, glabrous. Seeds winged, oblong, 0.5-1.4 mm. 2n = 24.

Flowering Jun-Aug. Dry to moist, subarctic, arctic, and alpine tundra, coastal marshes; 0-2500 m; Greenland; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Maine, N.H., N.Y., Wash., Wyo.; n, c Europe; n Asia.

Kalmia procumbens is the only species of the genus that is not endemic to North America. An attractive dwarf shrub, it is sometimes cultivated in rock gardens.