Japanese Elm
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| iJapanese Elm | ||||||||||||||
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 Japanese Elm, aged 30 years
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| Ulmus davidiana var. japonica Rehd. |
Japanese Elm Ulmus davidiana var. japonica (syn U. japonica) now also includes Wilson's Elm (formerly treated as U. wilsoniana C. K. Schneider) and U. propinqua Koidzumi (Fu, 2002). The species is one of the larger and more graceful Asiatic elms, endemic to much of continental north-east Asia and Japan. It commonly grows to over 30 m tall, with a broad crown comprising pendent branches. Augustine Henry described one tree at Iwimigawa railway station, Japan, as being 34 m tall, with a clean stem to a height of approximately 15 m (Elwes & Henry, 1913). The young shoots often bear corky wings, similar to those of the European Field Elm U. minor, to which it is closely related.
The leaves are generally obovate, up to 110 mm long, and with a coarse upper surface. The tree flowers in early spring, before the leaves appear. The samarae are obovate to orbicular, 15 mm long.
The tree was introduced to North America in 1895 as seed sent from Sapporo to the Arnold Arboretum, Massachusetts, whence seedlings were donated to Kew Gardens, London, two years later. The Arnold Arboretum specimens grew rapidly, and first flowered aged 12 years. Unlike many Asiatic species, Japanese Elm has also proven tolerant of a mild, maritime climate with high rainfall over winter.
Specimens planted at the Sir Harold Hillier Gardens in Hampshire, England, in 1977 have grown very well on heavy clay in an open location. In trials elsewhere in Hampshire, the tree also proved tolerant of dry soils on chalk, although growth was comparatively slow. Other living specimens are held in the UK at the Royal Botanic Garden Edinburgh, NCCPG elm collection [1] at Brighton & Hove, and at the Royal Horticultural Society Gardens at Wisley. In the USA, it is still grown at the Arnold Arboretum, and at the Holden Arboretum.
Resistant to Dutch elm disease and elm leaf beetle[2], the tree was assessed in Canada as a substitute for native elms that had succumbed. Consequently a number of particularly hardy cultivars were released there in the 1980s; they included Discovery[3], Freedom, Jacan, Mitsui Centennial, and Thomson. Two cultivars have been raised in the USA: Prospector, formerly treated under Wilson's Elm, and Emerald Sunshine formerly treated under U. propinqua Koidzumi.
[edit] References
- Bean, W. J. (1981). Trees and shrubs hardy in Great Britain. 7th edition. Murray, London.
- Brookes, A. H. (2006). An evaluation of disease-resistant hybrid and exotic elms as larval host plants for the White-letter Hairstreak butterfly, Satyrium w-album. Part 1. Butterfly Conservation, Lulworth, England.
- Burdekin, D. A. & Rushforth, K. D. (revised by Webber, J. F., 1996). Elms resistant to Dutch elm disease. Arboricultural Research Note 2/96. Arboricultural Advisory & Information Service, Alice Holt Lodge, Farnham, England.
- Elwes, H. J. & Henry, A. (1913). The Trees of Great Britain & Ireland. Vol. VII. pp 1848-1929. Private publication. [4]
- Fu, L., Xin, Y. & Whittemore, A. (2002). Ulmaceae, in Wu, Z. & Raven, P. (eds) Flora of China, Vol. 5 (Ulmaceae through Basellaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis, USA. [5]
