An evergreen shrub up to 15 ft high in the wild; young shoots covered with a short grey felt. Leaves oblanceolate, slenderly pointed but tapering more gradually towards the base, 2 to 41⁄2 in. long, 1⁄4 to 1 in. wide, dark green, glabrous above at maturity, clothed beneath with a loose grey felt; stalk 1⁄4 to 1⁄2 in. long. Flowers produced in March or April in clusters of five to eight on downy stalks 3⁄4 in. long. Calyx small, shallowly lobed, downy. Corolla bell-shaped, five-lobed, 2 to 21⁄4 in. wide, 13⁄4 to 2 in. deep, pink to pale rosy-lilac, spotted with maroon on the three upper lobes. Stamens ten, the longest about as long as the corolla, their stalks white, downy at the base; anthers dark brown. Ovary and base of style clad with white down, the latter nearly 2 in. long. Seed-vessel 3⁄4 in. long, covered with tawny down. (s. Arboreum ss. Argyrophyllum)
Native of W. Szechwan, China; discovered and introduced by Wilson in 1908. A distinct species on account of its stiff, very narrow leaves, grey-white beneath. It is perfectly hardy at Kew, but increases slowly in size because of its being so frequently cut back by late spring frosts, and for the same reason flowers there infrequently. It flowered with Lt-Col. Stephenson Clarke at Borde Hill, Sussex, in March 1918. Related to R. floribundum, it differs in its smaller, narrower leaves, more slenderly tapered at the base. It is named after the Hunnewell family, well known and ardent patrons of horticulture and botany in Massachusetts.