| Ulmus 'Urban' | |
|---|---|
 'Urban',Royal Bath & West showground, Shepton Mallet, UK | |
| Genus | Ulmus |
| Hybrid parentage | U. pumila × '148' (U. pumila ×U. minor '28') |
| Cultivar | 'Urban' |
| Origin | US |
Ulmus 'Urban' is an Americanhybridelmcultivar selected from the progeny of a controlled crossing of theSiberian ElmUlmus pumila (female parent) with the Dutch clone '148' (U. × hollandica 'Vegeta' ×U. minor '28')[1][2] in 1958 by Toru Arisumi of theUSDA atColumbus,Ohio. Clone '148' had been sent to the US from the Netherlands in 1952 by Johanna Went, leader of the elm research team at the Willie Commelin Scholten Phytopathology Laboratory in Baarn.[3]
'Urban' is considered a poor ornamental, the tree possessed of stiff branching and amorphous form.[4] Thelanceolate toobovate leaves are < 9 cm long × < 4 cm broad, smooth with light venation on the upper surface, on 6 mmpetioles and clustered on short, very thin, wingless branchlets.
'Urban' has a moderate resistance toDutch elm disease; in trials conducted by theIstituto per la Protezione delle Piante, Florence, it suffered 49.5% defoliation and 36.5% dieback when inoculated with spores of the causal fungus, compared with 2.8% and 1.2% resp. for'Sapporo Autumn Gold'.[5]Foliage was adjudged "resistant" toBlack Spot by the Plant Diagnostic Clinic of theUniversity of Missouri[2].However, foliage can be heavily to severely damaged by the Elm Leaf BeetleXanthogaleruca luteola[6][7][8][9]
Noted for its tolerance of poor soils, pollution, and drought, 'Urban' was one of a number of elm hybrids assessed by theForestry Commission in theUK in the 1970s; half a dozen trees were among a batch of elms donated by the Commission in 1981 to reinforce a shelter belt at theRoyal Bath & West showground[3] south ofShepton Mallet[4]. All these trees initially grew strongly on the heavy clay loam, attaining > 8 m in height in seven years. However, at this age, one died ofDutch Elm Disease whilst four others exhibited weakness at the root and fell in gales in later years.[10] Only one tree remains (theTROBI champion); 12 m high, 26 cmd.b.h. in 1997,[11] and that in poor health in 2008. However, the trees are survived by numerous root suckers.
Other plantings in Europe are few and far between; several were established in the port area ofAmsterdam[5]. The tree also featured in trials[6], inCanberra, Australia, started in 1988 but "has not shown promise in that environment".
'Urban' was crossed with the Wilson's Elm (now treated asJapanese ElmU. davidiana var.japonica) cultivar'Prospector' to create the cultivar'Patriot'.