Sitka mountain-ash (western mountain ash)
Rosaceae (Rose family)
Introduction to Vascular Plants
Map
Distribution of Sorbus sitchensis var. grayi
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Species Information
General:
Medium to tall shrub, 1-4 m tall; stems several, erect to spreading, sparingly branched, greyish-red; winter buds and young growth not sticky, somewhat rusty-hairy.
Leaves:
Alternate, deciduous, pinnately compound; leaflets 7 to 11, oblong to oblong-egg-shaped, 2-7 cm long, rounded to blunt at the tip, smooth above, sometimes rusty-hairy below, rather coarsely saw-toothed for not more than 3/4 their length.
Flowers:
Inflorescence a half-rounded, branched cluster of numerous (15 to 80) small flowers, the branches often minutely rusty-hairy; corollas white to cream, the petals 5, oval, 4-6 mm long; calyces mostly smooth, 5-lobed, the lobes triangular; ovaries inferior; stamens 15-20.
Fruits:
Berry-like pomes (like miniature apples), nearly globe-shaped to ellipsoid, 8-10 mm long, red, glaucous, 2- to 5-chambered; seeds 1 or 2 per chamber.
Notes:
Two sympatric varieties occur in BC:
1. Leaflets entire or toothed mostly above midlength................ var. grayi (Wenzig) C.L. Hitchc.
1. Leaflets toothed one-half to three-quarters their length................. var. sitchensis
USDA Species Characteristics
Flower Colour:
White
Blooming Period:
Late Spring
Fruit/Seed characteristics:
Colour: Red
Present from Summer to Fall
Source: The USDA
Ecology
The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)
| Site Information |
Value / Class |
||
|
Avg |
Min |
Max |
|
| Elevation
(metres) |
1064 | 1064 | 1064 |
| Slope
Gradient (%) |
55 | 55 | 55 |
|
Aspect (degrees) |
317 | 318 | 318 |
| Soil
Moisture Regime (SMR) [0 - very xeric; 4 - mesic; 8 - hydric] |
3 | 3 | 3 |
| Modal
Nutrient Regime
Class |
B | ||
| #
of field plots species was recorded in: |
1 | ||
| Modal
BEC Zone Class |
ICH | ||
|
All BEC Zones (# of stations/zone) species was recorded in |
ICH(1) | ||
|
Source:
Klinkenberg 2013
|
|||
Habitat and Range
Mesic to moist open forests, forest edges, streambanks, rockslides, thickets and meadows in the montane to alpine zones; common throughout BC (except NE BC), especially southward; N to AK and YT, E to AB and S to ID, MT and N CA.Synonyms
Synonyms and Alternate Names:
Sorbus occidentalis (S. Watson) Greene
Sorbus sitchensis subsp. grayi (Wenzig) Calder & Roy L. Taylor
Taxonomic Keys
1. Plants becoming trees over 5 m tall; leaflets usually more than 13, winter buds covered with long soft-hairy grey hairs; styles 2 or 3...........................S. aucuparia
1. Plants shrubby, usually less than 5 m tall; leaflets rarely as many as 13, winter buds not covered with long soft grey hairs; styles 3 to 5. 2. Winter buds rusty-hairy; calyces smooth on outside; leaflets blunt or rounded at the tip, toothed for not more than 3/4 of their length; styles 4 or 5, fruit red, glaucous...............S. sitchensis 2. Winter buds sticky, sparsely white-hairy; calyces hairy on outside; leaflets sharp-pointed at tip, toothed for most of their length; styles 3 or 4; fruit orange, not glaucous................S. scopulina Source: Illustrated Flora of British Columbia |