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A shrub or small tree in the wild, up to about 40 ft high and 1 ft in diameter of trunk; young shoots grey with down; winter-buds ovoid, silky, 1⁄2 in. or slightly more long. Leaves pinnate, 6 to 10 in. long; leaflets mostly in five or six pairs, well-spaced on the rachis, which is tinted with crimson or purple. Lateral leaflets up to 31⁄2 in. long and 1 to 11⁄2 in. wide, lanceolate or lanceolate-oblong, gradually pointed, dark green and slightly glossy above, coated beneath with white hairs which have been partly shed by autumn, margins finely to rather jaggedly serrate; lateral veins in twelve to sixteen pairs, impressed above and prominent beneath. Flowers opening in May or early June, about 1⁄2 in. wide, white, borne in flat or slightly convex corymbs up to 5 in. wide, the inflorescence-branches, pedicels and receptacles clad in grey down; stipules of the leaves immediately below the inflorescence large and leafy, fan-shaped, toothed at the apex, persistent in the fruiting stage. Petals roundish, with a short claw. Styles three or four. Fruits ripening in October, bright red or orange-yellow in the wild, sometimes deep yellow on cultivated trees, about 1⁄4 in. wide. Bot. Mag., t. 9403.
Native of W. Szechwan, China; discovered and introduced by Wilson. He first sent seed in 1908 during his first expedition for the Arnold Arboretum, collected in the Mupin area, but plants from this introduction were not widely distributed in Britain (at least not as S. esserteauiana, see below). During his second expedition Wilson sent two batches of seed from farther north (W.4156 and 4321), and from the herbarium specimens he collected at the same time Koehne described S. conradinae, which is the name under which plants from the second introduction were distributed. Koehne admitted that S. conradinae and S. esserteauiana (also described by him) were allied, and distinguished the former by the whiter and denser down beneath the leaflets, by their greater relative width, and their more deeply impressed veins. However, J. R. Sealy, writing in the Botanical Magazine in 1935, concluded that the characters relied on by Koehne were not of specific value, and united the two species under the name S. esserteauiana, a judgement that has not been seriously challenged since.
S. esserteauiana, as usually seen in gardens, has a short trunk dividing into a few stems which are set with long spurs throughout their length but sparsely branched. The fruits ripen late and may persist until January; the yellow-fruited forms are the most desirable. The leaves turn red before falling, though not on dry soils. Award of Merit 1934 (yellow-fruited) and 1958 (red-fruited).
Although there is no doubt that S. conradinae is synonymous with S. esserteauiana, the decision to unite them was challenged by Dr Fox on the grounds that a plant grown by him at Winkworth under the name S. conradinae differed from S. esserteauiana in a number of respects, notably that it branched more freely, had broader leaflets less hairy beneath and ripened its fruits as early as August, bearing them in more abundant trusses (Journ. R.H.S., Vol. 79 (1954), p. 92 and Fox MS). But if this sorbus is not S. esserteauiana, neither is it S. conradinae. In fact, it bears a strong resemblance to S. pohuashanensis but is more likely to be a hybrid of garden origin between S. esserteauiana and S. aucuparia. The tree in the Winkworth Arboretum that Dr Fox had in mind cannot be traced, but there is a specimen from it in the Kew Herbarium, and a similar tree at Borde Hill in Sussex, which was received as S. conradinae from the nursery attached to Vicary Gibbs’ collection at Aldenham.
There is a sorbus in cultivation which may derive from the original introduction of S. esserteauiana by Wilson in 1908, differing from the common form (previously grown as S. conradinae) in its relatively narrower leaflets less hairy beneath and less impressed veins. It has been grown as “S. wilsoniana” and has also been misidentified as S. pohuashanensis.
S. ‘Kew Hybrid’. – This fine rowan was put into commerce by Messrs J. O. Sherrard and Son of Newbury, Berks. It appears to be a hybrid of S. esserteauiana, of which the other parent could be either S. pohuashanensis or S. aucuparia. It is very free-flowering and bears heavy trusses of orange-red fruits 5⁄16 to 3⁄8 in. wide, ripening in September; the autumn colour is orange and purple. Mr Sherrard tells us that the original tree in the nursery was planted by his father in 1947 and is now about 23 ft high (1977). The provenance is unknown, but it is tempting to suppose that it was propagated from the tree at Kew that received an Award of Merit in 1948 (see ‘Kewensis’, under S. pohuashanensis).
S. ‘Warleyensis’. – This sorbus received an Award of Merit as Pyrus sp. when shown by Miss Ellen Willmott on October 6, 1931, and was later named S. sargentiana var. warleyensis by Marquand (Gard. Chron., Vol. 94 (1933), p. 177). It had been raised at Warley Court from seeds collected in China by one of the French missionaries and presented to Miss Willmott’s mother by Henri de Vilmorin. ‘Warleyensis’ scarcely belongs to S. sargentiana and is really nearer to S. esserteauiana, though the leaflets are more finely toothed than is usual in that species. It is probably no longer in cultivation, though ‘Kew Hybrid’ (see above) is near to it. Plants distributed in the 1930s under the name “S. aucuparia Warleyensis” are not S. ‘Warleyensis’ and are near to S. pohuashanensis; they were presumably propagated from some other plant at Warley Court.
S. wilsoniana Schneid. S. expansa Koehne – Although the name S. wilsoniana used to occur frequently in horticultural literature it is doubtful if the species to which the name properly belongs was ever introduced. It bears some resemblance to S. esserteauiana, but the leaflets are at first clad beneath with a dense white wool, later becoming almost or wholly glabrous.