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Sorbus

Sorbus commixta - Chinese scarlet rowan

Chinese scarlet rowan grows over a wide range in eastern Asia, particularly in Japan and generally in mountainous areas. This very variable species was described for science by the Swedish rowan expert Theodor Hedlund. The first specimens were planted in Finland in the late 1950s but it has been commercially available only since the 1990s and is still rare, despite being both attractive and hardy.

The species varies throughout its range, growing as either a shrub or a tree up to about 10m, with erect branches. The buds are somewhat sticky and the leaflets of the compound leaves are long-pointed and double-toothed. Both leaves and flowers of this species are usually larger than those of the native rowan (S. aucuparia).

Another difference from the native species is in the autumn colour, which is a magnificent burst of scarlet or glowing wine-red on the Chinese rowan. Mustila provides a good opportunity to compare the habit and autumn colour of trees of various provenances, with specimens from Sachalin, Hokkaido and central Korea. They are all growing well but the variations between them are large.

 

Sorbus aucuparia - rowan, mountain ash

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We meet this friend almost everywhere in Finland, from rocky islets to stony ridges and right up into the Lapland Fells. The rowan or mountain ash grows further north than any other naturally growing member of the Sorbus genus. Finns have always valued it; it was regarded as sacred by their forefathers, and felling such a tree was believed to bring misfortune to the house. In a survey in the 1980s it was discovered that the species grows in every fourth garden in Finland.

A typical pioneer tree, it starts growing quickly in early summer. It also ceases growth early, with the formation of a bud at the tip of the leading shoot, after which it starts gathering strength for new growth the following season. The mountain ash produces corymbs of white, scented flowers in early summer. After pollination, the flowers develop into almost round dark red to orange berries, edible to both birds and man, though usually rather bitter.

The wood of the mountain ash is fairly hard and tough and has been important in traditional handicrafts. It might come as a surprise to many that as firewood it produces more heat than the traditionally favoured birch.

 

Sorbus aria - common whitebeam

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At first sight, with the undersides of its white-felted leaves flickering in the wind, the common whitebeam doesn’t much resemble the typical mountain ash. Nevertheless it is a member of the large Eurasian genus of mountain ash (Sorbus), though there are many dendrologists who would like to see the whitebeams separated completely as their own genus of Aria. Typical of all 27 whitebeams species is that the leaves are (more or less) entire.

The common whitebeam is small to medium in size, with an attractive round to broadly egg-shaped habit. It has large (to 12 cms) leaves, the undersides white-haired, the base rounded, the tip more pointed. As the leaves break from their buds in spring they briefly resemble opening magnolia flowers. The flowers corymbs, which are also white-felted, open later in summer, when the leaves are fully open. Autumn leaf colour is yellow, the oval fruit ripening from green through yellow to orange and red.

When raised from seed, common whitebeam is very variable, depending on origin. Popular in Europe as a street tree, many varieties have been produced, e.g. 'Majestica' and ' Magnifica'; the young leaves of the variety 'Lutecens' is grey-felted on both upper and lower surfaces.

 

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