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A small, bushy tree rarely 40 ft high, with a short, grey, fluted trunk; young shoots at first furnished with pale hairs. Leaves oval or ovate, 2 to 4 in. long, 1 to 2 in. wide; rounded or heart-shaped at the base, taper-pointed, sharply and often doubly toothed; covered with white silky hairs when quite young, becoming sparsely hairy above, downy on the midrib and vein-axils beneath; stalk 1⁄4 to 1⁄2 in. long, downy. Male catkins 1 to 11⁄2 in. long. Fruiting clusters about 3 in. long; the bracts three-lobed, 1 to 11⁄2 in. long; the middle lobe much the largest and nearly 1 in. wide, toothed (often on one side only).
Native of eastern N. America and Mexico; introduced in 1812. Although very similar to the European hornbeam it is not so fine a tree, growing more slowly and never attaining to so large a size. Its leaves turn a deeper, more orange-yellow, or even scarlet shade in autumn. In winter, the best distinction between the two species is afforded by the buds; these, in our native hornbeam, are slender and spindle-shaped, 1⁄4 in. or more long, and like small beech buds, but they are egg-shaped and only 1⁄8 in. long in the American one. The tallest example at Kew, planted in 1916, measures 40 × 21⁄2 ft (1967); there are four others of about the same age, averaging 30 × 2 ft.
The bracts of the fruiting catkins in this species bear some resemblance to those of C. betulus but are less symmetrical, the inner margin being less toothed than the outer, or even entire, and the lobe at the base on this side is smaller than on the outer side. It is probably more closely allied to the Japanese C. laxiflora than it is to C. betulus.
specimens: Kew, pl. 1916, 40 × 21⁄2 ft (1967); Westonbirt, Glos., in Clay Island, 42 × 21⁄2 ft (1980); Bodnant, Gwyn., above Pin Mill, 30 × 3 ft (1981).
This species was described by Bean (B506, S143) and Krüssmann (K279).
Subsp. virginiana has an ovate to elliptical leaf, 8–12 cm long, with a caudate or acuminate apex and brown glands on the lower surface. The secondary teeth on the margins are almost as long as the primary teeth. In contrast, the type has an oblong to ovate leaf, 3–8.5 cm long, with an acute or obtuse apex and no abaxial glands. The secondary teeth are small and blunt. Furlow 1997. Distribution CANADA: Ontario, Quebec; USA: from Maine and Michigan south to Georgia and west to eastern Oklahoma. Habitat In the under storey of deciduous forests in wet areas, between 0 and 300 m asl. USDA Hardiness Zone 3b. Conservation status Not evaluated. Illustration NT202. Taxonomic note The ranges of the two Northern American subspecies of C. caroliniana overlap, and hybrids with intermediate features are common. The very similar species C. tropicalis (Donn. Sm.) Lundell occurs in tropical Central America and has been collected there (for example, by Allen Coombes in Veracruz, 1995), but is very tender.
American botanists seldom make a distinction between varieties of their native Carpinus caroliniana, which seems reasonable, but subsp. virginiana is the more northerly variant. It is an attractive multistemmed tree that forms a rounded, broad dome, with good yellow autumn colour rather earlier than C. betulus. There are identified specimens at Kew (6 m tall by 6 m wide since 1969) and the Arnold Arboretum, but in most collections the subspecies is not acknowledged.