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[].
Sorbus is treated here in the broad sense, including the subgenera Aria and Torminaria. However, these two subgenera are likely to be recognized at generic rank, based on flower and fruit characters, once molecular studies can consistently resolve their placement within the Pyrinae, overcoming current difficulties with interfertility, reticulate relationships, rapid radiation, and small samples[].
The taxonomy of Sorbus is complicated by apomixis, polyploidy, and hybridization among sections and genera, especially in Eurasia. Sorbus hybridizes with several other genera in the tribe Maleae, including Amelanchier (×Amelasorbus Rehder); Crataegus (×Crataegosorbus Makino); Aronia (×Sorbaronia C. K. Schneider); Cotoneaster (×Sorbocotoneaster Pojarkova); Pyrus (×Sorbopyrus C. K. Schneider), and Malus (×Tormimalus Holub [= Sorbus subg. Torminaria × Malus])[].

Common Name: Western Mountain Ash

General Information

Sorbus scopulina is a deciduous shrub usually growing 1 - 5 metres tall, occasionally to 8 metres. It usually produces 1 - 8 main stems[].
The plant is harvested from the wild for local use as a food and a medicine.

Known Hazards

Although no specific information has been seen, the seed, and other parts of the plant, is likely to contain cyanogenic glycosides. When injested, these compounds break down in the digestive tract to release cyanide. Used in small quantities in both traditional and conventional medicine, this exceedingly poisonous compound has been shown to stimulate respiration, improve digestion, and promote a sense of well-being[]. It is also claimed by some to be of benefit in the treatment of cancer - though this claim has been largely refuted.
In larger concentrations, however, cyanide can cause gasping, weakness, excitement, pupil dilation, spasms, convulsions, coma and respiratory failure leading to death[].
The levels of toxin can be detected by the level of bitterness:- sweet almonds, for example, contain only very low levels of it and are safe to eat in quantity, whilst bitter almonds (which are used as a flavouring in foods such as marzipan) contain much higher levels and should only be eaten in very small quantities. Great caution should be employed if the taste is moderately to very bitter[].

Botanical References

, ,

Range

Western N. America - Alaska to Northwest Territories, south to California and New Mexico

Habitat

Mountain slopes, open forests, forest edges, riparian zones, lakeshores; at elevations up to 3,300 metres[].

Properties

Edibility Rating
Medicinal Rating
Habit	Deciduous Shrub
Height	4.00 m
Pollinators	Insects
Cultivation Status	Wild

Cultivation Details

Sorbus scopulina is a very cold-hardy tree, tolerating temperatures down to around -25°c when dormant
Succeeds in most reasonably good soils in an open sunny position[]. Dislikes dry soils[]. Tolerates light shade[], though it fruits better in a sunny position[].
Plants are susceptible to fireblight[].

Edible Uses

Fruit - raw, cooked in pies, preserves etc, or dried for later use[, , ]. A bitter flavour[]. The fruit becomes sweeter and so tastes best after a frost, it can also be bletted if it is going to be eaten raw[]. This involves storing the fruit in a cool dry place until it is almost but not quite going rotten. At this stage the fruit of many species has a delicious taste, somewhat like a luscious tropical fruit. The bright orange to reddish orange, globose, subglobose, broadly obovoid, or broadly elliptic fruit is 8 - 12mm × 7.5 - 12mm[].

Medicinal

An infusion of the branches has been given to young children with bed-wetting problems[].
The bark is febrifuge and tonic[]. It has been used in the treatment of general sickness[].

Other Uses

The wood is soft and weighs 37lb per cubic foot[].

Propagation

Seed - best sown as soon as it is ripe in a cold frame[, ]. If you have sufficient seed it can be sown in an outdoor seedbed[, ]. Stored seed germinates better if given 2 weeks warm then 14 - 16 weeks cold stratification[], so sow it as early in the year as possible. Prick out the seedlings into individual pots when they are large enough to handle. Seedlings are very slow to put on top-growth for their first year or two[], but they are busy building up a good root system. It is best to keep them in pots in a cold frame for their first winter and then plant them out into their permanent positions in late spring.