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A small tree up to 60 ft high, with a slender trunk supporting a rounded head of branches; branchlets very slender, clothed with a close, minute, grey down; winter buds small, conical. Leaves leathery, 3⁄4 to 21⁄2 in. long, 1⁄3 to 11⁄3 in. wide, oval, ovate or obovate, unequally rounded at the base (or one side of the midrib tapered), pointed, the margins rather evenly toothed, the teeth triangular, often blunt, upper surface lustrous green, and smooth on the smaller twigs, rather rough on vigorous shoots, lower surface pale, bright green, with tufts of down in the vein-axils, or smooth; stalk 1⁄16 to 1⁄4 in. long, downy, veins in ten to twelve pairs. Flowers produced in September and October in the leaf-axils. Samaras ovate-oval, 1⁄3 in. long, not downy; seed in the centre.
Native of E. Asia, including Japan and much of China; introduced towards the end of the 18th century. This tree retains its leaves until the New Year quite fresh and green, and is well worth growing for its elegance. It is sometimes confused with U. pumila in gardens, but that species flowers in spring. From the other autumn-flowering elms, U. crassifolia and U. serotina, it is distinct in retaining its leaves so late, in the almost complete absence of down from beneath the leaves, and in their brighter smoother surfaces. Introduced in 1794.
This autumn-flowering species was described by Bean (B651) and Krüssmann (K411); we discuss it here too, however, as it has become very important in the fight against DED, to which it is largely resistant. Michael Dirr (1998) rates it extremely highly (and has personally been responsible for several selections), considering it to be one of the great landscape trees for a diversity of purposes. Its common name comes from its exfoliating bark, which can be very ornamentally coloured or relatively drab. It is very variable in all its characteristics, including leaf retention and hardiness, and suitability for geographical area should be borne in mind when choosing between clones. The standard sources provide lists of cultivars. Four that were selected for special mention by Warren (2000), and have also received general approval from Dirr (1998) and Jacobson (1996), are: ‘Emer I’ (sold as Athena), originating in Georgia and noted for outstanding bark and a rounded crown of dark green leaves (that unfortunately turn an unpleasing brown in autumn); ‘Emer II’ (sold as Allee), also from Georgia, highly rated for its excellent bark and good autumn colour, but with a more upright crown shape; and ‘A. Ross Central Park’ (sold as Central Park Splendor) – one of the hardiest clones, selected from an old tree in New York’s Central Park, with a broadly vase-shaped crown and good bright green leaves that turn yellow, although with dull bark. On ‘Dynasty’ opinions differ, Warren and Jacobson considering it to be a useful, fast-growing cultivar with good shape and decent autumn colour, though dull bark, but Dirr dissenting, claiming that it ‘borders on a boondoggle’ and citing poor shape and its boring bark as reasons not to grow it. With such a range of cultivars available in North America, it is unfortunate that European nurseries currently seem to offer only dwarfish and/or variegated clones. Opinions on these are best kept private.