5. Rhododendron lapponicum (Linnaeus) Wahlenberg, Fl. Lapp. 104. 1812.
Azalea lapponica Linnaeus, Sp. Pl. 1: 151. 1753
Shrubs, to 0.5(-0.7) m, rhizomatous. Stems prostrate to erect; bark ± smooth to vertically furrowed, shredding; twigs with straw-colored to ferruginous, multicellular, broad-rimmed, peltate scales and unicellular-hairy. Leaves persistent; petiole with broad-rimmed, glandular-peltate scales; blade oblong-elliptic to elliptic, ovate, or obovate, 0.4-2(-2.5) × 0.2-0.7 (-0.9) cm, coriaceous, margins entire, plane to revolute, with broad-rimmed scales, apex obtuse to rounded or mucronate, surfaces with conspicuous, straw-colored or golden to ferruginous, broad-rimmed, glandular-peltate scales and unicellular-hairy abaxially. Floral bud scales ferruginous-lepidote, sometimes also unicellular-hairy abaxially, margins ± ciliate, unicellular and multicellular, elongate eglandular-hairy. Inflorescences fasciculate racemes, 3-6-flowered; bracts similar to bud scales. Pedicels 2.5-14 mm, with ferruginous scales and often unicellular-hairy. Flowers opening before development of leaves, erect to horizontal, fragrant; calyx lobes 0.5-2 mm, with ferruginous scales and unicellular-hairy, margins ciliate, unicellular and multicellular eglandular-hairy; corolla rose to purple, sometimes white, without blotch, broadly funnelform, (6.5-)7.5-14(-15) mm, glabrous on outer surface, petals connate (for 3/4+ their lengths), lobes 4.5-8.5 mm, tube gradually expanding into lobes, 1.5-6.5 mm; stamens 5-10, slightly exserted, ± unequal, 7-13 mm; filaments glabrous or proximally unicellular-hairy. Capsules borne on erect pedicels, 4-7 × 2-3 mm, with ferruginous, peltate scales and unicellular-hairy. Seeds without distinct tails; testa closely appressed. 2n = 26, 52.
Flowering spring-summer. Arctic and alpine tundra, rocky barrens and heaths or thickets, raised beach ridges, sandy stream banks; 0-1900 m; Greenland; Alta., B.C., Man., Nfld. and Labr. (Nfld.), N.W.T., N.S., Nunavut, Ont., Que., Yukon; Alaska, Maine, N.H., N.Y., Wis.; Europe (Russia, Scandinavia); Asia (Siberia).
Rhododendron lapponicum is known to hybridize with R. tomentosum in Greenland, producing R. ×vanhoeffenii Abromeit.