10. Sorbus sitchensis M. Roemer, Fam. Nat. Syn. Monogr. 3: 139. 1847.
Shrubs, 10–40 dm. Stems 1–8; bark initially reddish purple to brownish gray, becoming grayish red; winter buds red-purple to red-brown, conic to ovoid, 8–13 mm, dull, ˂slightly glaucous˃, not glutinous, sparsely or densely villous, hairs primarily rufous. Leaves pinnately compound; stipules persistent, sometimes deciduous, hairs rufous; blade paler abaxially, dull blue-green, usually slightly glaucous, rarely faintly shiny adaxially, leaflets 7–13, opposite, sometimes subopposite, oblong to narrowly elliptic, sometimes oblanceolate, ovate, or obovate, 1.8–6 × 0.6–2.5 cm, l/w ratio 1.9–3.5, margins entire or finely to coarsely serrate, sometimes doubly serrate, apex obtuse or acute, surfaces soon glabrous, leaf and leaflet axils hairy, hairs rufous. Panicles 12–80-flowered, rounded, 2–8 cm diam.; peduncles glabrous, glaucous, or sparsely to densely villous, hairs primarily rufous. Pedicels glabrous, glaucous, or sparsely to densely villous, hairs primarily rufous. Flowers 11–17 mm diam.; hypanthium glabrous, ˂glaucous˃, hypanthium plus sepals 3–4 mm; sepals 1–2.2 mm, margins lightly to moderately ciliate, ˂hairs rufous or whitish˃, infrequently glandular; petals white, rarely pinkish, rhombic to ovate, 4–7.5 mm; stamens 15–20; carpels distinct, apex concave, depressed, or slightly conic and truncate, styles 3–5, 1.5–3.2 mm. Infructescences glabrous, glaucous, or villous. Pomes pinkish red or red (often appearing slightly purplish), subglobose to broadly elliptic or obovoid, 7–13 × 7–13 mm, dull, glaucous; sepals inconspicuous, incurved. Seeds red-brown, ovoid to ovoid-lanceolate, oblong or elliptic, 3.4–5 × 2.2–2.9 mm, symmetric or trigonous, slightly flattened.
Varieties 2 (2 in the flora): w North America
The other western Sorbus with rufous indument in the leaf and leaflet axils is S. californica, which differs in its smaller, shinier leaflets, less hairy inflorescences, and shiny winter buds. The winter buds of S. sitchensis are hairier and less scaly at the summit, also glaucous and never shiny or glutinous. In the field, the fresh fruits of S. sitchensis are often pinkish red; fruits of S. californica and S. scopulina are generally orange-red.