A deciduous shrub or a tree up to 40 ft high; young shoots covered with star-shaped down. Leaves lanceolate, tapered towards both ends, slender-pointed, toothed; 21⁄2 to 6 in. long, 1 to 21⁄2 in. wide; rich green above, pale and very downy beneath; stalks 1⁄6 to 1⁄2 in. long. Inflorescence a terminal, solitary, one-sided raceme, 4 to 6 in. long, 1 to 11⁄2 in. wide. Flowers white, tinged yellow, 1⁄2 in. wide, closely set on the raceme, each on a stalk 1⁄4 to 1⁄2 in. long, opening in July. Calyx-lobes ovate, pointed, 1⁄8 in. long, felted with grey down, turning rose-coloured after the petals have dropped. Petals rounded and notched at the end, sufficiently erect to form a cup-shaped flower; stamens about half as long as the petals, slightly hairy; anthers brown; ovary grey with down. Bot. Mag., t. 8970.
Native of Yunnan, China; discovered by Delavay in 1884; introduced by Forrest in 1913. I first saw it in flower in 1920, when the late Sir John Ross of Bladensburg sent it from his garden at Rostrevor, Co. Down, and was much impressed by its beauty. The racemes often take a more or less horizontal direction. Except for the evergreen C. arborea described above, this is probably the finest of all the clethras. It is unfortunately not quite hardy enough to grow out-of-doors at Kew, and after several trials has had to be relegated to a cool greenhouse. It thrives admirably in Sussex at Wakehurst Place, Nymans and Borde Hill, and at Minterne in Dorset. At Kilbryde in Northumberland, planted in 1927, it ‘has given no trouble. Flowering in July adds greatly to its value and these last two rather wet summers seemed to have been to its liking’ (R. B. Cooke in Journ. R.H.S., Vol. 92, 1967, p. 85 and fig. 40).
On one of Forrest’s wild specimens (12914) the leaves are 6 in. by 23⁄4 in. and the inflorescence 7 in. by nearly 2 in. It is at once distinguishable from C. fargesii and C. monostachya by its short stamens. In both those species they are longer than the petals.