Rhododendron columbianum

Shrubs or trees, to 2 m, rhizomatous. Stems: bark smooth, sometimes peeling or shredding with age; twigs unicellular-hairy, papillate, with flattened, glandular scales (lepidote). Leaves persistent, (fragrant when crushed); petiole with glandular-peltate scales without broad rim and few, ferruginous, long-crisped hairs; blade (white or pale green abaxially), ovate to lanceolate, (1-)2-8 × 1.5-3 cm, coriaceous, margins entire, plane, glabrous, apex usually acute, abaxial surface sparsely to densely papillate, with few, ferruginous, long-crisped hairs and glandular-peltate scales without broad rim, adaxial surface with scattered lepidote scales and/or papillae, sometimes also unicellular-hairy along midrib. Floral bud scales with peltate scales without broad rim and unicellular-hairy abaxially, margins unicellular-hairy. Inflorescences slightly rounded, 10-35-flowered; bracts lepidote abaxially, margins ciliate, unicellular-hairy. Pedicels 4-25 mm, with dense to sparse, ferruginous, long-crisped, unicellular and/or peltate scales, sometimes also long-stalked, multicellular glandular-hairy. Flowers radially symmetric, opening after leaves (of flowering shoots), ± erect, fragrance not noticeable at mid day; calyx lobes (often reflexed in fruit), ± 1-1.5 mm, outer surface densely to sparsely unicellular-hairy (hairs tan) and multicellular stipitate-glandular-hairy (hairs red) on margins; corolla white to cream, without blotch, ± rotate, 2-8 mm, inner surface hairy proximally, outer surface glabrous, petals appearing distinct or only slightly connate basally, lobes (4-)5-7 mm; stamens (8-)10 (-12), exserted, ± equal, 4.5-8.4 mm. Capsules borne on recurved pedicels, 2.5-5 × 2-6 mm (only slightly longer than wide), glabrous, acropetally dehiscent. Seeds somewhat elongated beyond narrow ends; testa closely appressed. 2n = 26.

Flowering spring-mid summer. Bogs, swamps, stream margins, sometimes on well-drained sites; 0-3500 m; Alta., B.C.; Calif., Colo., Idaho, Mont., Nev., Oreg., Utah, Wash., Wyo.