''Ulmus davidiana'' var. ''japonica'' 'Thomson' is a hardy, cold-resistant

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...

of the

Japanese Elm Japanese elm is a common name for several plants and may refer to: * ''Ulmus davidiana'' var. ''japonica'' *''Zelkova serrata ''Zelkova serrata'' (Japanese zelkova, Japanese elm or keyaki or keaki; ja, 欅 (ケヤキ) keyaki /槻 (ツキ) tsu ...

assessed by the

Prairie Farm Rehabilitation Administration The Prairie Farm Rehabilitation Administration (PFRA) was a branch under Agriculture and Agri-Food Canada (AAFC), a department of the Federal Government of Canada. The Prairie Farm Rehabilitation Administration was established by an Act of Parliam ...

(PFRA) Nursery (now the AAFC-PFRA&E Shelterbelt Centre) at

Indian Head Indian Head can refer to: Coins * Indian Head cent, U.S. one cent coin (1859–1909) *Indian Head eagle, U.S. $10 gold piece issued between 1907 and 1933 *Indian Head gold pieces, U.S. coins issued between 1908 and 1929 *Indian Head nickel, U.S. f ...

Saskatchewan Saskatchewan ( ; ) is a Provinces and territories of Canada, province in Western Canada, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...

, in the 1970s as part of its shelterbelt tree research.Lindquist, C. H. & Howe, J. A. G. (1979). Thomson Elm. ''Canadian Journal of Plant Science'' 59:1159
/ref>Schroeder, W. (1994). Genetic improvement for prairie tree plantings. ''Journal of Arboriculture''. 20(1), Jan. 1994.
The tree was one of a number of Japanese Elms planted in an experimental shelterbelt at Indian Head in 1953. These shelterbelt trees were derived from seed taken from two openly pollinated Japanese Elms obtained from

Manchuria Manchuria is an exonym (derived from the endo demonym " Manchu") for a historical and geographic region in Northeast Asia encompassing the entirety of present-day Northeast China (Inner Manchuria) and parts of the Russian Far East (Outer Manc ...

and planted at Indian Head in 1929. 'Thomson' attained a height of 8 m in 25 years, a rather modest performance compared with Siberian Elm ''

Ulmus pumila ''Ulmus pumila'', the Siberian elm, is a tree native to Asia. It is also known as the Asiatic elm and dwarf elm, but sometimes miscalled the 'Chinese Elm' (''Ulmus parvifolia''). ''U. pumila'' has been widely cultivated throughout Asia, Nor ...

'' and American Elm '' Ulmus americana'' grown at the same site. Nevertheless, the tree has proved exceptionally hardy.

Description

'Thomson' is distinguished by a single trunk bearing a vase-shaped crown, the branches forming strong wide-angled crotches; the bark is dark grey and deeply fissured. The twigs have diamond-shaped fissures that become more apparent on second-year wood, and occasionally sport corky wings. The leaves are borne on 1 cm petioles, and average 7.5 cm in length, obovate to elliptic, with the typical acuminate apex and oblique base; dark green and glabrous, they turn bright yellow in autumn. The

samara Samara ( rus, Сама́ра, p=sɐˈmarə), known from 1935 to 1991 as Kuybyshev (; ), is the largest city and administrative centre of Samara Oblast. The city is located at the confluence of the Volga and the Samara (Volga), Samara rivers, with ...

e are obovate and deeply notched at the apex. The species does not sucker from roots.

Pests and diseases

'Thomson' displayed a resistance to Dutch elm disease when inoculated by Dr E. S. Kondo of the Canadian Forest Service (CFS) in

Sault Ste. Marie Sault Ste. Marie is a cross-border region of Canada and the United States located on St. Marys River, which drains Lake Superior into Lake Huron. Founded as a single settlement in 1668, Sault Ste. Marie was divided in 1817 by the establishment of ...

; the original tree still survives (2008) and has also proven resistant to elm leaf beetle '' Xanthogaleruca luteola''. Moreover, the tree's foliage was adjudged "resistant" to Black Spot by the Plant Diagnostic Clinic of the

University of Missouri The University of Missouri (Mizzou, MU, or Missouri) is a public university, public Land-grant university, land-grant research university in Columbia, Missouri. It is Missouri's largest university and the flagship of the four-campus Universit ...

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Cultivation

The tree was usually propagated by grafting on Siberian Elm seedlings. Released for sale in Saskatchewan in 1980, 'Thomson' is no longer in commerce owing to restrictions imposed by the Canadian government on the movement of elms across the country, which severely limited its potential market. 'Thomson' was never introduced to Europe or Australasia.

Synonymy

*'Thompson': In error for 'Thomson'.

Etymology

The tree was named for Mr W. B. Thomson, appointed director of PFRA in 1973.

Accessions

;North America * Royal Botanical Gardens (Ontario), Royal Botanical Gardens, Burlington, Ontario; one tree, planted c.1980.Photographs of 'Thomson' at Royal Botanical Gardens, Burlington, Ontario; ''U. davidiana'' var. ''japonica''; worldplants.ca
/ref>

References

{{DEFAULTSORT:Ulmus Davidiana Var. Japonica 'Thomson' Japanese elm cultivar Ulmus articles missing images Ulmus