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A shrub of bushy, vigorous habit, from 5 to 10 ft high; branchlets covered with down, which persists over the winter. Leaves narrowly obovate or oval, tapering at both ends; 11⁄2 to 31⁄2 in. long, 1⁄2 to 3⁄4 in. wide; the margins set with even, black-tipped teeth; upper surface dark dull green, with dark glands along the midrib; lower surface covered with a thick grey felt, which remains until the leaf falls; stalk 1⁄3 in. or less long. Flowers white or slightly rosy, about 1⁄2 in. across, produced during late May in small corymbs. Fruit globular or rather pear-shaped, 1⁄4 in. wide, bright red.
Native of eastern N. America; cultivated in England since 1700. It is a variable plant (Loudon describes some nine or ten forms), and has hybridised with A. melanocarpa. It is found under several names in gardens, and is confused with A. melanocarpa. That species, however, in its typical form, is well distinguished by its glabrous or nearly glabrous leaves and black fruits. The foliage of several forms of A. arbutifolia, especially one grown in nurseries as “erythrocarpa”, turns a brilliant red before falling. The species is indeed worth growing for its autumn colour alone.
Between this species and A. melanocarpa comes A. prunifolia (Marsh.) Rehd., also offered in nurseries under Spach’s name “floribunda” and as the “purple-fruited chokeberry”. It is intermediate between the other two species but, we are told by Dr Rehder, not a hybrid. The dark purple fruits furnish the best distinction.
Hardin’s conclusion is that A. prunifolia (page 327) is not an independent species, but rather the product of hybridisation between A. arbutifolia and A. melanocarpa. These two species, which in ancient times occupied separate areas, came into contact and interbred when they migrated northward after the Ice Age, and have continued to interbreed up to the present time. Owing to the ability of these hybrids to set seed without fertilisation, they can ‘breed true’ and thus simulate a species. A. prunifolia is therefore a hybrid complex, which is at its most variable in places where the parental species are in contact. Spach’s A. floribunda (Pyrus floribunda Lindl.) is very like A. prunifolia and probably represents a form of the hybrid that arose in cultivation. Hardin also remarks that there is no certain way of distinguishing A. prunifolia from pure A. melanocarpa.