Ulmus davidiana var. japonica 'Thomson'

Elm cultivar

Ulmus davidiana var. japonica 'Thomson'
Variety	Ulmus davidiana var. japonica
Cultivar	'Thomson'
Origin	PFRA Nursery, Saskatchewan, Canada

Ulmus davidiana var. 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] [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.

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 samarae are obovate and deeply notched at the apex.

The species does not sucker from roots. ^[4]

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; 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 [3].

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

None known.

References

^ Lindquist, C. H. & Howe, J. A. G. (1979). Thomson Elm. Canadian Journal of Plant Science 59:1159
^ Schroeder, W. (1994). Genetic improvement for prairie tree plantings. Journal of Arboriculture. 20(1), Jan. 1994.
^ Burdekin, D.A.; Rushforth, K.D. (November 1996). "Elms resistant to Dutch elm disease" (PDF). Arboriculture Research Note. 2/96. Revised by J.F. Webber. Alice Holt Lodge, Farnham: Arboricultural Advisory & Information Service: 1–9. ISSN 1362-5128. Retrieved 26 October 2017.
^ Heybroek, Hans M. (1981). "The Japanese elm species and their value for the Dutch elm breeding program" (PDF). Proceedings of the Dutch Elm Disease symposium and workshop, October 5–9, Winnipeg, Manitoba: 78–90.

Elm species, varieties, hybrids, hybrid cultivars and species cultivars

Species, varieties and subspecies

U. alata (Winged elm)
U. americana (American elm)
U. americana var. floridana (Florida elm)
U. bergmanniana (Bergmann's elm)
U. bergmanniana var. bergmanniana
U. bergmanniana var. lasiophylla
U. castaneifolia (Chestnut-leafed or multinerved elm)
U. changii (Hangzhou elm)
U. changii var. changii
U. changii var. kunmingensis (Kunming elm)
U. chenmoui (Chenmou or Langya Mountain elm)
U. chumlia
U. crassifolia (Cedar or Texas cedar elm)
U. davidiana (David or Father David elm)
U. davidiana var. davidiana
U. davidiana var. japonica (Japanese elm)
U. elongata (Long raceme elm)
U. gaussenii (Anhui or hairy elm)
U. glabra (Wych or scots elm)
U. glaucescens (Gansu elm)
U. glaucescens var. glaucescens
U. glaucescens var. lasiocarpa (hairy-fruited glaucescent elm)
U. harbinensis (Harbin elm)
U. ismaelis
U. laciniata (Manchurian cut-leaf or lobed elm)
U. laciniata var. nikkoensis (Nikko elm)
U. laevis (European white elm)
U. laevis var. celtidea
U. laevis var. parvifolia
U. laevis var. simplicidens
U. lamellosa (Hebei elm)
U. lanceifolia (Vietnam elm)
U. macrocarpa (Large-fruited elm)
U. macrocarpa var. glabra
U. macrocarpa var. macrocarpa
U. mexicana (Mexican elm)
U. microcarpa (Tibetan elm)
U. minor (Field elm)
U. minor subsp. minor
U. minor var. italica
U. parvifolia (Chinese or lacebark elm)
U. parvifolia var. coreana (Korean elm)
U. prunifolia (Cherry-leafed elm)
U. pseudopropinqua (Harbin spring elm)
U. pumila (Siberian elm)
U. rubra (Slippery elm)
U. serotina (September elm)
U. szechuanica (Szechuan (Sichuan) or red-fruited elm)
U. thomasii (Rock or cork elm)
U. uyematsui (Alishan elm)
U. villosa (Cherry-bark or marn elm)
U. wallichiana (Himalayan or kashmir elm)
U. wallichiana subsp. wallichiana
U. wallichiana subsp. xanthoderma
U. wallichiana var. tomentosa

Disputed species, varieties and subspecies

U. boissieri
U. minor subsp. canescens (Grey, grey-leafed or hoary elm)
U. elliptica

Hybrids

U. davidiana var. japonica × U. minor
U. × arbuscula
U. × arkansana
U. × brandisiana
U. × diversifolia
U. × hollandica (Dutch elm)
U. × hollandica var. insularum
U. × intermedia
U. × mesocarpa

Species cultivars

American elm	American Liberty Ascendens Augustine Aurea Beaverlodge Beebe's Weeping Brandon Burgoyne JFS Prince II College Columnaris Creole Queen Deadfree Delaware Exhibition Fiorei Flick's Spreader Folia Aurea Variegata Great Plains Hines Incisa Independence Iowa State Jackson Jefferson Kimley Klehmii L'Assomption Lake City Lewis & Clark Littleford Maine Markham Miller Park Minneapolis Park Moline Morden New Harmony Nigricans Patmore Pendula Penn Treaty Princeton Pyramidata Queen City Sheyenne Skinner Upright St. Croix Star Valley Forge Variegata Vase Washington
Cedar elm	Brazos Rim
Chinese elm	A-1 A. Ross Central Park Blizzard BSNUPF Burgundy Burnley Select Catlin Chessins Churchyard Cork Bark D. B. Cole Drake Dynasty Ed Wood Elsmo Emer I Emer II Emerald Prairie Frosty Garden City Clone Geisha Glory Golden Rey Hallelujah Hokkaido Jade Empress King's Choice Littleleaf Lois Hole Matthew Milliken Nire-keyaki Ohio Orange Ribbon Pathfinder Pendens Prairie Shade Prince Richard Red Fall Sabamiki Sagei Seiju Select 380 Sempervirens Small Frye State Fair Stone's Dwarf Taiwan The Thinker Todd True Green UPMTF Ware's Yarralumla Yatsubusa Zettler Ulmus parvifolia f. lanceolata
European white elm	Aureovariegata Colorans Helena Ornata Pendula Punctata Urticifolia
Field elm	Ademuz Albo-Dentata Amplifolia Argenteo-Variegata Atinia Atinia Pyramidalis Atinia Variegata Bea Schwarz Biltii Christine Buisman Concavaefolia Coritana Cretensis Cucullata Cucullata Variegata Dehesa de Amaniel Dehesa de la Villa Dicksonii Dijkwel Erecta Folia Alba-Punctata Glandulosa Goodyeri Hoersholmiensis Holmstruph Hunnybunii Hunnybunii pseudo-Stricta Laciniata Lanuginosa Majadahonda Microphylla Pendula Microphylla Purpurea Microphylla Rubra Monumentalis Pendula Picturata Plotii Propendens Punctata Purpurascens Purpurea Retiro Reverti Rugosa Rueppellii Sarniensis Schuurhoek Silvery Gem Sowerbyi Stricta Suberosa Umbraculifera Gracilis Umbraculifera Viminalis Viminalis Aurea Viminalis Betulaefolia Viminalis Gracilis Viminalis Incisa Viminalis Marginata Viminalis Pendula Viminalis Pulverulenta Viminalis Stricta Virgata Webbiana
Japanese elm	Discovery Freedom Jacan JFS-Bieberich Mitsui Centennial Prospector Reperta Reseda Thomson Validation
Siberian elm	Ansaloni Aurea Aurescens Chinkota Dropmore Dwarf Weeper Green King Hansen Harbin Manchu Mauro Mr. Buzz Park Royal Pendula Pinnato-ramosa Poort Bulten Puszta Pyramidalis Fiorei Zhonghua Jinye
Winged elm	Lace Parasol
Wych elm	Albo-Variegata Australis Camperdownii Cebennensis Concavaefolia Cornuta Corylifolia Purpurea Corylifolia Dovaei Fastigiata Macrophylla Fastigiata Stricta Fastigiata Variegata Firma Flava Gigantea Gittisham Grandidentata Holgeri Horizontalis Insularis Latifolia Latifolia Aurea Latifolia Aureo-Variegata Latifolia Nigricans Luteo Variegata Lutescens Macrophylla Maculata Minor Nana Nigra Nitida Oblongata Pendula Macrophylla Pendula Variegata Pyrenaica Spectabilis Superba Tomentosa

Hybrid cultivars

Androssowii Amsterdam Arno Cathedral Clusius Columella Den Haag Dodoens Escaillard Fiorente Frontier Fuente Umbria Homestead Karagatch Lobel Morfeo Morton Morton Glossy Morton Plainsman Morton Red Tip Morton Stalwart Nanguen New Horizon Patriot Plantyn Plinio Rebella Rebona Recerta Regal Repura Revera San Zanobi Sapporo Autumn Gold Sapporo Gold 2 Stavast Toledo Urban Wanoux Wingham
Dutch elm	Alba Angustifolia Balder Belgica Blandford Canadian Giant Cicestria Cinerea Commelin Dampieri Dauvessei Daveyi Dumont Elegantissima Eleganto-Variegata Etrusca Fastigiata Fjerrestad Folia Rhomboidea Freja Fulva Gaujardii Groeneveld Haarlemensis Klemmer Loke Macrophylla Aurea Major Microphylla Modiolina Muscaviensis Odin Pioneer Pitteurs Serpentina Smithii Superba Tricolor Tyr Vegeta Viminalis Viscosa Wentworthii Pendula Wredei Ypreau
U. × intermedia	Coolshade Fremont Improved Coolshade Lincoln Rosehill Willis