Sorbus scopulina
Sorbus sambucifolia
Cascade mountain-ash, Greene's Mountain ash, mountain ash, Rocky Mountain ash, Rocky Mountain Mountain ash, Rocky Mountain or Cascade Mountain ash, Rocky Mountain or Cascade or Greene's Mountain Ashe, western mountain-ash
Aleutian Mountain ash, Siberian Mountain ash
1–8;
bark gray, sometimes yellowish or reddish purple, or grayish red;
winter buds olive brown to red-brown, conic, 8–14 mm, shiny, slightly glutinous, glabrous or sparsely or densely whitish-villous.
1–8;
bark gray;
winter buds blackish red to black, conic, 7–18 mm, shiny, slightly glutinous, sparsely villous distally, hairs primarily rufous.
pinnately compound;
stipules deciduous or persistent, hairs whitish;
blade paler abaxially, shiny, green to dark green adaxially, leaflets 7–13(–15), opposite or subopposite, lanceolate, oblong, narrowly ovate, oblanceolate, or obovate, (3–)4–6.5(–8.7) × 1.5–2.7 cm, l/w ratio 2.1–4.4, margins finely serrate, apex obtuse, acute, or acuminate, surfaces glabrous, leaf and leaflet axils hairy, hairs whitish.
pinnately compound;
stipules sometimes persistent, margins and surface hairy, hairs rufous;
blade paler abaxially, shiny, green to dark green adaxially, leaflets 7–11, opposite or subopposite, lanceolate, sometimes narrowly elliptic, elliptic, oblong, or oblanceolate, 2.5–6.5 × 0.9–2.5 cm, l/w ratio 1.9–3.8, margins serrate, apex usually acute to acuminate or attenuate, sometimes obtuse, surfaces soon glabrous;
leaf and leaflet axils hairy, hairs rufous.
40–200+-flowered, flat-topped to rounded, 5–15 cm diam.;
peduncles sparsely to densely whitish-villous.
6–23-flowered, rounded, 2.5–7 cm diam.;
peduncles sparsely rufous-villous.
sparsely to densely whitish-villous (in flower and fruit).
sparsely rufous-villous.
11–13 mm diam.;
hypanthium nearly glabrous or densely villous, hypanthium plus sepals 3–4 mm;
sepals 0.8–2.3 mm, margins lightly to densely whitish-villous, glands absent or sparse and usually inconspicuous;
petals white, ovate, 4–6 mm;
stamens (14–)20;
carpels distinct, apex conic, styles 3 or 4, 2–2.5 mm.
10–15 mm diam.;
hypanthium glabrous, hypanthium plus sepals (4.5–)5–6 mm;
sepals 1.5–2.9 mm, margins usually villous, hairs white and reddish mixed [white], rarely sparsely glandular;
petals white to pinkish, orbiculate or ovate, 4–5 mm;
stamens 20;
carpels almost completely adnate to hypanthium, apex truncate or slightly conic, styles 4 or 5, 1.5–3.5 mm.
whitish-villous, rarely glabrous with age.
glabrous.
bright orange to reddish orange, globose, subglobose, broadly obovoid, or broadly elliptic, 8–12.1 × 7.5–12.8 mm, shiny, sometimes lightly glaucous;
sepals inconspicuous, incurved.
red, ellipsoid, 10–12 × 7–9 mm, shiny, not glaucous;
sepals prominent, erect.
brown, narrowly ovoid, 3.8–5.4 × 1.7–2.8 mm, slightly asymmetric, slightly flattened.
dark brown, lanceoloid, 4 × 2 mm, symmetric, not flattened.
= 34, 68.
= 34 (Asia).
Sorbus scopulina
Sorbus sambucifolia
Sorbus scopulina is variable, especially in leaflet shape, number, and indument. Plants with narrower leaflets were separated as S. angustifolia; plants with broader leaflets were segregated as S. andersonii and S. cascadensis. Densely hairy forms were named S. dumosa. All represent points on a morphologic continuum, united by their shiny leaflets, whitish indument, and western range. Sparsely hairy forms approach the more southern S. californica but have whitish axillary hairs and larger leaflets than that species, which has rufous axillary hairs and leaflets less than 4 cm. Most S. scopulina have shiny hypanthia and fruits. Occasional collections, all within the range of S. sitchensis, are glaucous-fruited. This may be natural variation, or it could represent introgression from S. sitchensis. H. A. McAllister (2005, pers. comm.) found that individuals of S. scopulina from cordilleran Idaho and Arizona were sexual diploids; plants from the Cascade and Coast ranges of British Columbia and Washington were tetraploid and presumably apomictic. Here, these entities are synonymized, awaiting a larger study that might correlate distinct morphologic characteristics with the ploidy levels. J. J. Aldasoro et al. (1998, 2004) noted that some European Sorbus species are both diploid and tetraploid, suggesting that sexual species occasionally produce spontaneous agamospermous individuals.
The intergeneric hybrid ×Amelasorbus jackii Rehder [Amelanchier alnifolia (Nuttall) Nuttall ex M. Roemer × Sorbus scopulina] has been collected in Idaho and Oregon. Foliage of the Idaho collection is very similar to that of Amelanchier, with basal pinnae inconspicuous and infrequent, suggesting that this hybrid may be overlooked.
The illegitimate later homonym Sorbus alaskana G. N. Jones pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
In North America, Sorbus sambucifolia is known only from the four westernmost islands of the Aleutians, where it is allopatric from all other Sorbus. Sorbus scopulina is known from farther east in the Aleutians; sterile specimens differ in their whitish, not rufous indument, and the less deeply sunken reticulate venation on the adaxial surfaces of the leaflets.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
BC
CA
OR
WA
Flora NW
PNW Herbaria
SW CO Wildflowers
WildflowerSearch
iNaturalist
USDA Plants Database
