Clethra delavayi
Credits
Article from Bean's Trees and Shrubs Hardy in the British Isles
Recommended citation
'Clethra delavayi' from the website Trees and Shrubs Online (treesandshrubsonline.
Synonyms
- Clethra monostachya Rehder & E.H.Wilson
Editorial Note
Bean treated Clethra monostachya as a separate species. Hu (1960) distinguished C. monostachya from C. delavayi by its elliptic or ovate-elliptic or rarely lanceolate (not obovate) leaves, which are glabrous both sides (against uniformly tomentose beneath), and by its smaller flowers with pubescent styles. However, on the basis of the ‘strongly continuous pattern of variation’ in key characters across the species’ Chinese range, the Flora of China (2025) adopts a broad circumscription of C. delavayi that encompasses closely related species including C. monostachya (but not C. fargesii). The text below is adapted from Bean to reflect the updated taxonomy.
A fuller, revised treatment of the genus will be provided when funding is available. If you would like to sponsor this work please write to editor@treesandshrubsonline.org
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).
The form known under the name of C. monostachya was discovered by Wilson in W. Szechwan, China at 5,000 to 7,000 ft elevation and introduced by him to the Coombe Wood nursery in 1903. It has pure white flowers in usually solitary racemes up to 8 in. long and 1 in. wide, and is quite hardy (C. fargesii by contrast has racemes in clusters).
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 by its short stamens. In that species they are longer than the petals.