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])[
Pyrus sambucifolia Bong.
Pyrus sitchensis (M.Roem.) Piper
Sorbus occidentalis (S.Watson) Coville
Sorbus tilingii Gand.
Common Name: Sitka Mountain Ash
Sorbus sitchensis is a deciduous shrub that can grow from 1 - 4 metres tall, usually producing 1 - 8 main stems[
The plant is harvested from the wild for local use as a food, medicine and source of materials. It can be used as a pioneer for restoring native woodland.
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[
Western N. America - Alaska to California, east to Idaho and Montana.
Open conifer woods, forest edges, mountain slopes, meadows, shores of lakes and streams, rockslides, edges of avalanche tracks, peatlands, muskegs; mainly on rich, moist soils; at elevations up to 3,000 metres[
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Sorbus sitchensis 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[
]. This species is able to succeed in poor soils and to become established on exposed broken ground[
], it is thus suitable for use as a pioneer species in re-establishing woodland[
A slow-growing shrub in the wild, it can sometimes become a small tree up to 9 metres tall[
]. It usually produces abundant crops of fruit every year[
Plants are susceptible to fireblight[
Fruit - raw or cooked in pies, preserves etc[
]. Of poor quality[
]. The fruit turns sweeter and so tastes best after a frost[
]. The pinkish red or red (often appearing slightly purplish), subglobose to broadly elliptic or obovoid fruit is around 7 - 13mm × 7 - 13mm; the fruit being produced in clusters[
An infusion of the branches has been given to young children with bed-wetting problems[
An infusion of the root and branch bark has been drunk in the treatment of stomach problems and rheumatism[
]. The infusion can also be used externally as a bath for treating rheumatism[
]. A decoction of the root and branch bark has been used as an eyewash[
The bark has been chewed in the treatment of colds[
An infusion of the branches has been used in the treatment of weak kidneys in order to stop the frequent urination[
The berries have been rubbed onto the scalp in order to get rid of lice[
This species is capable of growing in exposed conditions in poor soils[
], and so could be used in re-afforestation as a pioneer plant to provide suitable conditions for other woodland trees to be established[
]. It is rather slow-growing, however, and would only be used in situations where faster species were not so suitable[
Wood - moderately light with little strength, it is of no commercial value[
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.