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A shrub, or more commonly a tree 25 to 40 ft high (said by Kingdon Ward to grow taller than this in the forests of N. Burma); young shoots stout, at first coated with brown and whitish hairs intermixed, later glabrous; winter-buds ovoid, 1⁄2 to 7⁄8 in. long, the outer scales glabrous except at the tip, the inner densely hairy. Stipules on sterile growths up to 1 in. wide and often persistent, toothed. Leaves up to 10 in. long with mostly two to five pairs of leaflets (but sometimes with a single pair and with up to seven or eight in KW 7746); rachis grooved, not winged; petiole with a wide, sheathing base, almost concealing the subtended bud. Leaflets leathery, oblong, mostly 2 to 5 in. long and 3⁄4 to 11⁄4 in. wide (but even larger on some Forrest specimens), more or less equal, but the basal pair sometimes smaller and more elliptic, apex subacute to obtuse or even retuse at the apex, oblique at the base, dark green and soon glabrous above, undersides (and rachis) at first coated with rusty and some whitish hairs, becoming glabrous except for a few hairs on the midrib, glaucous and papillose, margins often revolute and then apparently entire, but fine serrations evident when the leaflet is flat. Flowers small, creamy white, in convex clusters up to 6 in. wide; inflorescence-branches at first densely hairy, becoming glabrous or retaining a few white, spreading hairs, lenticellate. Petals roundish, about 1⁄8 in. wide. Styles two or three. Fruits globose, white, pink or purplish red, about 3⁄8 in. wide, in rather sparse clusters.
Native of the eastern Himalaya, east through upper Burma to S.W. Yunnan and bordering S.E. Tibet; described by Hooker in 1878 from Sikkim specimens but not introduced until Forrest sent seeds in 1912 from the Shweli-Salween divide near the border between Yunnan and Burma (F.9040); raised from this seed it flowered at Caerhays, Cornwall, in May 1924. Forrest later sent seed from other localities in the Burma-China borderland, and there was one sending by Farrer and Cox from the same area in 1921. Kingdon Ward sent seed in 1926 from the Seinghku valley, Burma, near the Assam frontier (KW 6851).
In its foliage, S. insignis is the most remarkable of the pinnate-leaved group of Sorbus, remote in aspect from the common rowan and suggesting some evergreen species from a subtropical rain-forest. The original Forrest introduction is very tender but a plant at Nymans in Sussex, probably from KW 6851, has survived there for about half-a-century.
The Yunnan-Burma forms of S. insignis have generally been known by the name S. harrowiana, described from a fruiting specimen collected by Forrest in 1912. Here, following Dr Hutchinson, this species is included in S. insignis. It is true that most specimens from Yunnan have fewer and larger leaflets than those of Sikkim (on some Forrest specimens they are 6 in. long and almost 2 in. wide), but the difference is not one on which to base two separate species, and is not constant.
More distinct from typical S. insignis (and from S. harrowiana) is the sorbus introduced by Kingdon Ward from Mt Japvo in the Naga Hills of Assam in 1927-8. This has long been grown as Sorbus sp. KW7746 (its field-number), but Dr Hutchinson, when working on Sorbus in the 1940s, identified it as S. insignis and his judgement has been upheld by other botanists. It agrees with S. insignis in most of its essential characters, but is certainly untypical in having up to seven or eight pairs of leaflets not more than 3 in. long, with brown hairs persisting on the midrib beneath. The deep pink fruits are borne in clusters of up to 100. It is hardier than the Forrest introductions.
S. ‘Bellona’. – So far a shrub of pyramidal habit about 10 ft high (1979). Winter-buds with rusty-hairy inner scales. Leaflets in three to five pairs, palish matt-green above, grey beneath, glabrous on both sides at maturity, narrowly oblong-obovate, toothed only in the upper one-third to one-half, 11⁄4 to 31⁄2 in. long and up to 1 in. wide. Fruits small, pale pinkish red, in trusses about 6 in. wide. Raised at Kew in 1956 from seeds received as S. harrowiana. Award of Merit September 7, 1971. It is evidently a hybrid of S. insignis but the other parent is uncertain.
S. ‘Ghose’. – A tree, ultimate height unknown. Young parts clad with a whitish or pale brown woolly indumentum that persists more sparsely on the undersides of the leaflets and in the inflorescence until the autumn. Leaflets in six to eight pairs, oblong or narrowly oblong-lanceolate, up to 21⁄2 in. long, serrate in the upper half, acute at the apex, oblique at the base, light matt-green above; petioles swollen at the base, but not sheathing the buds. Inflorescence about 6 in. wide, many-flowered, with stout main branches; stipules leafy, fan-shaped, toothed, persistent in some seasons. Fruits when nearly ripe dull crimson, eventually redder and glossy, 1⁄4 to 3⁄8 in. wide.
This interesting sorbus was raised by Messrs Hillier from seeds received from the Indian seedsman Ghose of Darjeeling. It seems to be intermediate between S. insignis and S. foliolosa (wallichii). It agrees in many respects with the description of S. arachnoidea Koehne, described from a specimen collected in Sikkim, and another from Chumbi, just across the border with Tibet, but these collections are not represented in the Kew Herbarium. Koehne likened his species to S. scalaris, with which ‘Ghose’ too has some affinity.