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.
Phenology: Flowering Jun–Aug.
Habitat: Dry to moist, subarctic, arctic, and alpine tundra, coastal marshes
Elevation: 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.