Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Philadelphus incanus' from the website Trees and Shrubs Online (treesandshrubsonline.
A shrub up to 8 ft or more high; young shoots more or less hairy. Leaves ovate or oval, broadly wedge-shaped or almost rounded at the base, slender-pointed, finely toothed, 21⁄2 to 4 in. long, 11⁄4 to 21⁄4 in. wide on the barren shoots; those of the flowering twigs mostly 1 to 2 in. long; upper surface set with sparse minute hairs, the lower one thickly covered with appressed pale, stiff hairs giving it a dull grey hue; stalk 1⁄12 to 1⁄2 in. long, bristly. Flowers white, fragrant, about 1 in. across, produced five to nine (usually seven) together on downy racemes about 2 in. long, at the end of leafy shoots of about the same length. Petals roundish; style about the average length of the stamens, glabrous, divided quite half-way down; disk glabrous. Calyx and flower-stalk shaggy, like the undersurface of the leaves. Fruits top-shaped, 3⁄8 in. long.
Native of W. Hupeh and Shensi, China; discovered by Henry about 1887 and introduced by Wilson in 1904. It flowers late – from middle to late July or even into August – and the species is desirable on that account. It is also charmingly fragrant with an odour like that of hawthorn.