Ulmus davidiana var. japonica 'Thomson' | |
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Variety | Ulmus davidiana var. japonica |
Cultivar | 'Thomson' |
Origin | PFRA Nursery, Saskatchewan, Canada |
Ulmus davidianavar.japonica 'Thomson' is a hardy, cold-resistant cultivar of the Japanese Elm assessed by the Prairie Farm Rehabilitation Administration (PFRA) Nursery (now the AAFC-PFRA&E Shelterbelt Centre) at Indian Head, Saskatchewan, in the 1970s as part of its shelterbelt tree research. [1] [2] . [3]
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 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 and American Elm Ulmus americana grown at the same site. Nevertheless, the tree has proved exceptionally hardy.
'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 samarae are obovate and deeply notched at the apex.
The species does not sucker from roots. [4]
'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; 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 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.
The tree was named for Mr W. B. Thomson, appointed director of PFRA in 1973.
None known.
Ulmus pumila, the Siberian elm, is a tree native to Central Asia, eastern Siberia, the Russian Far East, Mongolia, Tibet, northern China, India and Korea. It is also known as the Asiatic elm and dwarf elm, but sometimes miscalled the 'Chinese Elm'. It is the last tree species encountered in the semi-desert regions of central Asia. Described by Pallas in the 18th century from specimens from Transbaikal, Ulmus pumila has been widely cultivated throughout Asia, North America, Argentina, and southern Europe, becoming naturalized in many places, notably across much of the United States.
Ulmus davidiana var. japonica, the Japanese elm, is one of the larger and more graceful Asiatic elms, endemic to much of continental northeast Asia and Japan, where it grows in swamp forest on young alluvial soils, although much of this habitat has now been lost to intensive rice cultivation.
Ulmus 'New Horizon' is an American hybrid cultivar raised by the Wisconsin Alumni Research Foundation (WARF), from a crossing of the Japanese Elm clone W43-8 = 'Reseda' with Siberian Elm clone W426 grown from seed collected from a street tree at Yankton, South Dakota. Tested in the US National Elm Trial coordinated by Colorado State University, 'New Horizon' averaged a survival rate of 74% after 10 years.'New Horizon' was patented in the US in 1994, while in Europe, it is marketed as one of the 'Resista' elms protected under E U breeders' rights.
Ulmus macrocarpaHance, the large-fruited elm, is a deciduous tree or large shrub endemic to the Far East excluding Japan. It is notable for its tolerance of drought and extreme cold and is the predominant vegetation on the dunes of the Khorchin sandy lands in the Jilin province of north-eastern China, making a small tree at the base of the dunes, and a shrub at the top.
Ulmus szechuanicaFang, known as the Szechuan (Sichuan), or red-fruited, elm, is a small to medium deciduous Chinese tree found along the Yangtze river through the provinces of Sichuan, Jiangxi, Anhui, and Jiangsu.
Ulmus 'Clusius' is a Dutch hybrid elm cultivar raised at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen, and released to commerce in 1983. 'Clusius' was derived from a crossing of the same Dutch clones that produced the fastigiate 'Lobel' released in 1973: '202' and '336'.
Ulmus 'Homestead' is an American hybrid elm cultivar raised by Alden Townsend of the United States National Arboretum at the Nursery Crops Laboratory in Delaware, Ohio. The cultivar arose from a 1970 crossing of the Siberian Elm Ulmus pumila with the hybrid N 215, the latter grown from seed sent in 1960 to the University of Wisconsin-Madison elm breeding team by Hans Heybroek of the De Dorschkamp Research Institute in the Netherlands. Tested in the US National Elm Trial coordinated by Colorado State University, 'Homestead' averaged a survival rate of 85% after 10 years. 'Homestead' was released to commerce without patent restrictions in 1984.
Ulmus 'Urban' is an American hybrid elm cultivar selected from the progeny of a controlled crossing of the Siberian Elm Ulmus pumila with the Dutch clone '148' in 1958 by Toru Arisumi of the USDA at Columbus, 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.
Ulmus 'Morton Red Tip' is a hybrid cultivar raised by the Morton Arboretum from an open pollination of Accolade. The tree has occasionally been reported as a hybrid of Accolade with the Siberian Elm Ulmus pumila, an error probably owing to the commercial propagation of the tree by grafting onto U. pumila rootstocks. Tested in the US National Elm Trial coordinated by Colorado State University, Danada Charm averaged a survival rate of 77.5% after 10 years.
Ulmus 'Morton Stalwart', is a Morton Arboretum hybrid cultivar arising from a controlled crossing of Accolade with the hybrid of a Field Elm U. minor from eastern Russia and a Siberian Elm U. pumila. Tested in the US National Elm Trial coordinated by Colorado State University, Commendation averaged a survival rate of 85% after 10 years.
Ulmus 'Cathedral' is a hybrid cultivar raised at University of Wisconsin–Madison patented in 1994. Arising from a chance crossing of the Japanese elm and Siberian elm, seed was sent in 1958 by Prof. Nobuku Takahashi and his colleagues at the Sapporo Botanical Garden of Hokkaido University, Sapporo, to Eugene Smalley at Wisconsin–Madison; 'Cathedral' is thus a sibling of 'Sapporo Autumn Gold' and 'New Horizon'.
The American Elm cultivar Ulmus americana 'Valley Forge' was raised by the Agricultural Research Service in Maryland. The tree was released to wholesale nurseries without patent restrictions by the U. S. National Arboretum in 1995 after proving to have a high resistance to Dutch elm disease. 'Valley Forge' proved only moderately successful in the US National Elm Trial, averaging a survival rate of 66.7% overall, owing largely to environmental factors rather than susceptibility to disease.
The Japanese Elm cultivar Ulmus davidianavar.japonica 'Discovery' is a cold-resistant selection from Canada, raised along with 'Freedom' in the 1980s by Dr Wilbert Ronald, of Jeffries Nurseries Ltd. and Rick Durrand of Shade Consulting Services, Portage la Prairie, Manitoba.
The Japanese Elm cultivar Ulmus davidianavar.japonica 'Jacan' is a cold-resistant selection from Canada. The tree was raised by the Morden Research Station, Morden, Manitoba in the 1980s.
The hybrid elm cultivar Ulmus × intermedia 'Lincoln' was selected from crossings of the Slippery, or Red, Elm Ulmus rubra and the Siberian Elm Ulmus pumila made in Aurora, Illinois, circa 1958 and patented in 1983 by Samuel Clegg of Clegg Landscaping, Plainfield, IL and Charles McFarland of Urbana, IL.
The American elm cultivar Ulmus americana 'Lewis & Clark' is a development from the North Dakota State University (NDSU) Research Foundation breeding programme, released in 2004 to commemorate the 200th anniversary of the eponymous expedition. The cultivar was cloned from a tree discovered in 1994 along the Wild Rice River south west of Fargo, ND., where all those around it had succumbed to Dutch elm disease; the tree remains in perfect health (2008). Prairie Expedition proved only moderately successful in the US National Elm Trial, averaging a survival rate of 62.6% overall, owing largely to environmental factors rather than susceptibility to Dutch elm disease.
The Japanese elm cultivar Ulmus davidianavar.japonica 'Prospector' was originally treated as a cultivar of Wilson's elm U. wilsonianaSchneid., a species sunk as Ulmus davidiana var. japonica by Fu. A U.S. National Arboretum introduction, it was selected in 1975 from a batch of 1965 seedlings in Delaware, Ohio, and released without patent restrictions in 1990. 'Prospector' proved moderately successful in the US National Elm Trial, averaging a survival rate of 76% overall.
Ulmus 'Patriot' is a hybrid cultivar raised by the United States National Arboretum in 1980. Derived from a crossing of the American hybrid 'Urban' with the Wilson's Elm cultivar 'Prospector', 'Patriot' was released to commerce, free of patent restrictions, in 1993. Tested in the US National Elm Trial coordinated by Colorado State University, 'Patriot' averaged a survival rate of 85% after 10 years.
Ulmus parvifolia, commonly known as the Chinese elm or lacebark elm, is a species native to eastern Asia, including mainland China, Taiwan, Japan, North Korea, South Korea and Vietnam. It has been described as "one of the most splendid elms, having the poise of a graceful Nothofagus".
The American Elm cultivar Ulmus americana 'St. Croix' is a recent (2008) selection cloned from a large tree growing at Afton, Minnesota, which has displayed a high resistance to Dutch elm disease (DED). A U S patent, PP 20097, was granted in 2009.