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A deciduous shrub or small tree; young branchlets clad with short erect or appressed hairs, lenticellate; second-year stems with a close bark (but see cv. ‘Bretschneideri’). Leaves variable in shape, mostly ovate to broad-ovate, cuneate to rounded or sometimes cordate at the base, 31⁄2 to 8 in. long, 11⁄4 to 51⁄2 in. wide, serrate, glabrous or with scattered hairs above, the underside usually more or less densely coated with appressed or spreading hairs, but sometimes glabrous except for hairs on the veins; petiole 1⁄2 to 11⁄4 in. long. Inflorescence corymbose. Fertile flowers white, numerous, with usually ten stamens; ovary semi-inferior, i.e., its upper part projecting above the rim of the receptacle, which bears five triangular calyx-lobes about 1⁄10 in. long; styles two to four. Ray-flowers always present, white, 1 to 2 in. across. Capsules surmounted by the thickened bases of the styles and with the rim of the receptacle persisting at or slightly above the middle.
H. heteromalla ranges from the Himalayan region of Kumaon eastward and northward to western, west central and northern China. It was described from Nepal and introduced in 1821, though the present garden stock is wholly or for the most part of much more recent origin. It varies in leaf-shape and indumentum and numerous species have been made out of these variations, none of which is recognised by Miss McClintock – hence the long list of synonyms.
Before the publication of Miss McClintock’s monograph the name H. heteromalla was used in a narrower sense for a hydrangea fairly common in collections, with leaves 3 to 8 in. long, 11⁄2 to 3 in. wide, covered with a close tomentum beneath, with reddish petioles. It is of erect habit, flowers in July and August, and attains a height of 20 ft or more in the milder parts. It is quite hardy south of London and often produces self-sown offspring in great abundance. Other forms of the species were introduced from China by Wilson and by Forrest, but none of these are on the average any better than the more typical form of the species.
This was reintroduced by the University of North Wales Expedition to east Nepal in 1971 (B.L. & M. 222), and later by Roy Lancaster from Mount Omei in western Szechwan, China.