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A tree up to 70 or 80 ft high in a wild state; the bark of the trunk not peeling, dark, almost black; branchlets silky hairy when very young, soon becoming glabrous and shining brown. Leaves ovate or ovate-oblong, mostly heart-shaped at the base, pointed, 21⁄2 to 6 in. long, 11⁄2 to 31⁄2 in. wide, toothed (often doubly so), dark glossy green and ultimately glabrous above, paler green and silky-hairy on the midrib and veins beneath; veins in ten to thirteen pairs; leaf-stalk 1⁄4 to 1 in. long, hairy. Male catkins 2 to 3 in. long. Fruiting catkins 1 in. or rather more long, 1⁄2 in. in diameter, scarcely stalked; scales not downy, the lateral lobes rather wider than the middle one.
Native of eastern N. America, where it yields a valuable timber; introduced in 1759, according to Aiton. When bruised, the young bark has a sweet, aromatic taste and smell, and by distillation yields an aromatic oil. This birch is allied to B. lutea, but differs in the darker bark of the trunk, the sweeter-tasting young bark, and especially by the glabrous scales of the fruit catkin. In my experience it is not so well-doing a tree as B. lutea in this country.
It is not common in cultivation in the British Isles, but there are specimens 45 to 50 ft high at Tortworth, Glos.; Dawyck, Peebl.; and Mount Usher, Co. Wicklow, Eire.
This species has a more restricted distribution in the wild than its ally B. alleghaniensis (lutea), being rare in Canada and not extending beyond the Appalachians. By contrast B. alleghaniensis reaches as far to the north-west as the Great Lakes and some way beyond, and is well represented in south-eastern Canada.
specimens: Winkworth Arboretum, Surrey, 46 × 43⁄4 ft at 1 ft (1978); Hollycombe, Liphook, Hants, 62 × 63⁄4 ft (1984); Brocklesby Park, Lincs., 56 × 33⁄4 ft (1977); Tortworth, Glos., 56 × 33⁄4 + 31⁄4 ft (1979); Abbeyleix, Co. Laois, Eire, 52 × 4 ft (1985).
† B. uber (Ashe) Fern. B. lenta var. uber Ashe – Perhaps the rarest of all birches, this is known only from a single stand about one kilometre long and 100 metres wide, growing in the flood-plain of Cherry Creek, Smyth County, Virginia. It is allied to B. lenta but has smaller leaves on shorter petioles, shorter catkins, less pubescent and relatively longer-lobed bracts and smaller fruits. Fernald’s opinion that this species has some relationship with B. pumila is no longer accepted (Brittonia, Vol. 36, pp. 307-16 (1984); see also Castanea, Vol. 41, pp. 248-56 (1976)).
B. uber was introduced to the Royal Botanic Gardens, Wakehurst Place, Sussex, in 1984.
This species was described by Bean (B420, S114) and Krüssmann (K227).
B. uber (Ashe) Fernald
Although it was briefly described by Clarke (1988), we give here an expanded account of this intriguing and beautiful small tree. A thorough review of its status has been made by McAllister & Ashburner (2004) who convincingly demonstrate that, far from being a distinct species (Betula uber), it should be regarded as a genetic variant occurring occasionally in B. lenta. Among seedlings from wild-collected ‘B. uber’ seed, only one per cent replicated their parental characteristics; the rest were f. lenta (McAllister & Ashburner 2004). As B. uber it was the first tree to be listed as a ‘US Federally Endangered Species’, meaning that it cannot be collected or sold without a permit. This has not greatly restricted its occurrence in collections: in America it is represented in many arboreta as part of the conservation effort. There is one particularly nice specimen at Starhill Forest Arboretum; two tall (c.12 m) trees at the Morton Arboretum, however, are ageing and looking rather sparse. Its rarity has perhaps inhibited a more objective view of its true relationship with B. lenta, of which it can be said to be merely a form with small, rounded leaves (McAllister & Ashburner 2004). Its conservation status should be reviewed. Under any name, however, it is readily recognisable and is a tidy, compact tree with high horticultural merit – genuinely suitable for a small garden. The leaves turn the same bright yellow as B. lenta. There are good specimens in several collections in Europe, including 6 m trees at Thenford House and Herkenrode.