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A dwarf or prostrate shrublet 6 to 12 in. high, its stems rooting here and there, covered with a smooth, grey bark; winter buds ovoid, about 3⁄16 in. long, crimson, hairy towards the tip; young shoots very short, thinly hairy at first. Leaves 15⁄8 to 31⁄4 in. long, with four to seven pairs of leaflets; rachis scarcely winged, broadly grooved above. Leaflets oval, broadly oblong-elliptic to ovate-elliptic, 1⁄4 to 1⁄2 in. long and 3⁄16 to 5⁄16 in. wide, very sharply serrate, glabrous. Inflorescence with three to five pink flowers, crowded at the top of a hairy peduncle, the flowers sessile or on short stalks. Receptacle glabrous, purplish, obconical, about 1⁄8 in. long, its lobes ovate-triangular, also glabrous. Petals orbicular, about 1⁄12 in. wide. Stamens ten. Styles three to five. Fruits about 3⁄8 in. wide, glabrous.
A native of northwest Yunnan and northern Burma at altitudes of 10,000 to 13,500 ft. The type-specimen of S. poteriifolia was collected by its describer, the Austrian botanist, in 1916, on the Irrawaddy – Salween divide, at 12,500 to 13,000 ft, growing on micaceous schist, but Forrest had in fact collected it two years earlier, and did so on several occasions later. It was apparently not introduced until Kingdon Ward collected seeds in the Seingkhu valley, northwest Burma, in 1926 at 11–12,000 ft (KW 6968). He saw it in flower towards the end of June, and when he returned to collect seeds ‘its numerous clusters of reddened berries presently turned snow white, beading the crinkly black stems like moonstones.’ He sent seeds five years later from the neighbouring Adung valley, and also collected it during his last expedition to Burma in 1953.
Plants from KW 6968 were raised at Kew and one of these, six inches high, was shown to the Scientific and Floral B Committees of the Royal Horticultural Society on July 13, 1943, already in ripe fruit. At that time Dr Hutchinson considered the plant to be S. reducta (q.v.) and it was exhibited under that name. He later concluded that it was a new species, differing from S. reducta in its almost glabrous calyx-lobes, pink flowers and white fruits. It is also dwarfer, and semi-herbaceous. He had intended to publish a description of this new acquisition under the name S. pygmaea but he abandoned his studies of Sorbus later in 1943 and never did so, though the name was imparted to gardeners and came into use for the few plants then in cultivation. It has since proved, however, that S. pygmaea would have been a superfluous name for S. poteriifolia.
S. poteriifolia might have become extinct in gardens had not Harold Hillier kept some plants on his rock garden at Jermyns House, regrafting them whenever they had shown signs of weakening. Dr Hugh McAllister has raised seedlings from them in the Liverpool Botanic Garden, which agree perfectly with the parent, so this interesting species is becoming more widely available. The seedlings grow much better than the grafted parents.
As an authority on the classification and phylogeny of flowering plants, Dr Hutchinson was interested in S. poteriifolia and S. reducta as recently evolved and advanced species of the genus, approaching the herbaceous habit and with half the normal number of stamens.
Note. As first described by Handel-Mazzetti, S. poteriifolia included the element later separated by him under the name S. filipes, not treated here. The description given here also excludes specimen Forrest 20266, which Handel-Mazzetti continued to include in S. poteriifolia (see text). For the S. poteriifolia of gardens, see S. ‘McLaren D.87’, mentioned below.
S. ‘McLaren D. 84’ S. poteriifolia Hort., not Hand.-Mazz. – A tree so far about 30 ft high in gardens; edges of bud-scales, young growths, rachis and midribs of leaflets beneath all sparsely furnished with white hairs, the foliage becoming glabrous. Leaflets in mostly seven or eight pairs, 1 to 13⁄8 in. long, about 1⁄2 in. wide, oblong, sharply toothed to the base. Inflorescences broad, many-flowered, rather lax, the main branches up to 2 in. long, borne on clustered spurs. Stipules under the inflorescence awl-shaped to semi-ovate, up to 1⁄4 in. long, deciduous. Flowers pink. Fruits globose, deep rosy pink, about 3⁄8 in. wide.
This rowan was raised from seeds gathered by one of Forrest’s collectors, some of whom continued to work for some time after his death at Lord Aberconway’s expense. The seed was distributed as S. poteriifolia, but it is not that species. There are matching specimens among Forrest’s collections in Yunnan, especially from the Mekong-Salween divide, taken from trees up to 30 ft high, some with more numerous leaflets than in the cultivated plants. This rowan received an Award of Merit for its fruits when shown by the Crown Estate Commissioners, Windsor Great Park, on September 21, 1951.
The correct name for this species is uncertain, but it may be S. monbeigii (Cardot) Hand.-Mazz.