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Article from Bean's Trees and Shrubs Hardy in the British Isles
'Sorbus thibetica' from the website Trees and Shrubs Online (treesandshrubsonline.
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A tree to 50 ft high in the wild, but sometimes a shrub. It is allied to S. cuspidata but with often more slender branches and with smaller leaves, to about 5 in. long, variable in shape as are those of S. cuspidata but more often almost orbicular, and clad beneath with a looser tomentum (not almost plastered as in S. cuspidata); in some specimens identified as S. thibetica they are almost glabrous beneath. The flowers are somewhat smaller, and the styles are two or three in number (rarely fewer than four in S. cuspidata). The fruits, according to collectors’ notes are yellow with a red flush, or ‘green-orange’.
S. thibetica was described from a specimen collected by the French missionary Soulié in 189; in northwest Yunnan near the Tibetan border, and a photograph of the type-specimen is reproduced by Eleanora Gabrielian in her work on Sorbus, plate 42. Cardot described the fruits as dark red, a faulty inference as they were obviously immature (green, unripe fruits in this group become very dark when dry). S. thibetica appears to be fairly common in Yunnan, and to extend through Burma and the eastern Himalaya as far as central Bhutan (but other specimens from Bhutan seem to be S. cuspidata, which for its part extends as far as Burma at least).
Plants are in cultivation under the name S. thibetica KW 21175, raised from seeds collected by Kingdon Ward during his expedition in 1953 to The Triangle (the mountains between the two upper branches of the Irrawaddy). This has light brown young branchlets, they and both sides of the leaves thinly filmed with cobwebby hairs. The leaves are elliptic to broadly so or roundish, cuneate to almost truncate at the base, to about 5 in. long, shortly stalked, lateral veins in nine to ten pairs, straight and parallel, not much branched. Flowers very small and few in the inflorescence. Styles one to three, free. Fruits globular or broad-ellipsoid, up to 3⁄4 in. long, yellow or orange when ripe in late October, but quickly decaying to toffee-coloured, lenticellate. This tree really agrees better with S. wardii Merr., described from a flowering specimen collected by Kingdon Ward on an earlier expedition to Burma, but this species has been submerged in S. thibetica by Yü.
With a rather better claim to be called S. thibetica is a sorbus in the Westonbirt Arboretum, named S. ‘Mitchellii’ (‘John Mitchell’). The young stems are soon glabrous, very dark in their second year. Leaves broadly elliptic, ovate-elliptic or roundish, 4 to 5 in. long, 33⁄8 to 41⁄4 in. wide, truncate to rounded at the base, dark green and at first woolly above, silvery tomentose beneath, the felt looser than in S. cuspidata. Inflorescences 3 to 4 in. wide, loosely woolly. Flowers about 3⁄4 in. wide. Styles mostly two. Fruits brown when fully ripe in October, globular, about 5⁄8 in. or slightly more wide, lenticellate.
The original plant at Westonbirt was planted in 1938 and measures 64 × 43⁄4 ft (1975). It was raised there from seeds, which may well have been collected in Yunnan, since ‘John Mitchell’ closely resembles specimens collected there by Forrest and others. It is believed that the seeds were received as Pyrus vestita (S. cuspidata), but Forrest’s collections of S. thibetica were originally identified as that species.
This fine tree is named in honour of William John Mitchell, vmh, who was for many years curator of the Westonbirt Arboretum. There is an avenue in the Royal Horticultural Society’s Garden at Wisley, and also a specimen there on Weather Hill.
The name ‘Mitchellii’, being in Latin form and published after January 1, 1959, is not in accordance with the International Code of Nomenclature of Cultivated Plants. The rendering ‘John Mitchell’ is proposed here.
The original tree of ‘John Mitchell’, at Westonbirt, Glos., measures 70 × 51⁄4 ft (1980) and there is a younger tree of this clone, pl. 1953, at Stanway, Glos. Interestingly Alan Mitchell has found another specimen of S. thibetica at Alexandra Park, Hastings, Sussex in Bohemia Wood, which is of about the same age as the Westonbirt tree and measures 56 × 5 ft, with a fine bole (1983).