Ulmus 'Morton'

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Ulmus 'Morton'
Morton accolade elm.jpg
Accolade, Morton Arboretum, Illinois
GenusUlmus
Hybrid parentageU. davidiana var. japonica × U. davidiana var. japonica
Cultivar'Morton' = Accolade
OriginUS

Ulmus 'Morton' (selling name Accolade) is an elm cultivar cloned from a putative intraspecific hybrid planted at the Morton Arboretum in 1924, which itself originated as seed collected from a tree at the Arnold Arboretum in Massachusetts. Although this tree was originally identified as Ulmus crassifolia, it is now believed to have been a hybrid of the Japanese elm (Ulmus davidiana var. japonica) and Wilson's elm (formerly Ulmus wilsoniana, but also sunk as U. davidiana var. japonica).[1] Accolade has proven to be the most successful cultivar tested in the US National Elm Trial, averaging a survival rate of 92.5% overall.[2]

Description[]

The parent tree at the Morton Arboretum is noted for the resemblance of its habit to the American elm Ulmus americana, its upright-arching branches creating the familiar vase-shape, although the tree does not grow as large as the iconic native elm, reaching scarcely 20 m at maturity.[3] Its glossy, deep green leaves are also markedly smaller, rarely exceeding 8 cm in length. The tree is commercially propagated by grafting onto an Ulmus pumila rootstock.

Accolade has a propensity to produce co-dominant stems and major branches with bark inclusions, demanding corrective pruning on at least an annual basis where planted in towns.[4]

  • Accolade foliage, midsummer

  • American Elm (left) and Accolade leaf comparison

Pests and diseases[]

In its 90+ years, the original tree at Morton has survived three epidemics of Dutch elm disease there unscathed.[5] However, two trees included in trials at the University of Minnesota were found to be afflicted by the disease in 2004, although one appears to have recovered completely.[6] The cultivar has also proved to be highly resistant to elm yellows and the elm leaf beetle Xanthogaleruca luteola [1] [7] [2], but not to the Japanese beetle, which can cause extensive foliar damage.[8]

Cultivation[]

Accolade is reputed to grow well in almost all soils save those excessively wet, and is notably drought-tolerant and cold hardy. In artificial freezing tests at the Morton Arboretum[9] the LT50 (temp. at which 50% of tissues die) was found to be −35.5 °C. The tree grows vigorously at first, gaining as much as one metre per annum, but slows to approximately half that rate with maturity. Thus, a typical 20-year-old tree could be expected to have reached 14 m in height with a crown about 5 m in width.[10] Trees grown by , Michigan State University, at Novi were the most vigorous and robust of the 37 different cultivars and species under assessment, described as looking like 'men among boys'.[11] Accolade is being evaluated in the National Elm Trial[12] coordinated by Colorado State University. Accolade was introduced to Europe in 2006 and is now in commerce in the Netherlands.

Hybrid cultivars[]

Accolade was crossed with the hybrid cultivar 'Morton Plainsman' = Vanguard. A selection of the resultant seedlings was marketed under the name 'Charisma', later changed to 'Morton Glossy' = Triumph.

Synonymy[]

  • Thornhill Elm: Anon.

Accessions[]

North America
  • Arnold Arboretum, US. Acc. no. 130–2002
  • Bickelhaupt Arboretum, US. Acc. no. 98–051
  • Brenton Arboretum, US. No details available.
  • Chicago Botanic Garden, US. 3 trees, no other details available.
  • Dawes Arboretum,[13] US. 1 tree. No acc. details available.
  • Holden Arboretum, US. Acc. nos. 89–76, 91–114, 98–23, L–00–501
  • Morton Arboretum, US. Acc. nos. 2352–24, 255–74, 128–92, 272–97, 35–98, 280–2003. 495–2004, 1095–2004, 1246–2004, 1347–2004, 269–2008.[3][14]
  • , US. No acc. details.
  • Smith College, US. Acc. nos. 20304, 35804, 37505
  • University of Idaho Arboretum, US. 2 trees. Acc. no. 1998008.
  • University of Washington campus, US. 5 trees.[15]
Europe
  • Grange Farm Arboretum, UK. Acc. no. 503.
  • Great Fontley Farm, Fareham, UK. Butterfly Conservation Elm Trials plantation, Home Field, one small tree planted 2010.
  • Royal Botanic Garden Edinburgh, UK. Acc. no. 20021372

Nurseries[]

North America
  • Acorn Farms, Galena, Ohio, US.
  • Bailey Nurseries, St. Paul, Minnesota, US.
  • Carlton Plants, LLC, Dayton, Oregon, US.
  • Charles J. Fiore, Prairie View, Illinois, US.
  • ForestFarm, Williams, Oregon, US.
  • J. Frank Schmidt & Son Co., Boring, Oregon, US.
  • Johnson's Nursery, Menomonee Falls, Wisconsin, US.
  • Linder's Garden Center, St. Paul, Minnesota, US.
  • North American Plants, Lafayette, Oregon, US.
  • Pea Ridge Forest, Hermann, Missouri, US.
  • Sester Farms [3], Gresham, Oregon, US.
  • Sun Valley Garden Centre, Eden Prairie, Minnesota, US.
Europe
  • Batouwe Boomkwekerijen B.V., Dodewaard, Netherlands. Potted whips.
  • Boomkwekerij Gebr. Van den Berk B.V., Sint-Oedenrode, Netherlands.

References[]

  1. ^ Fu, L.; Xin, Y.; Whittemore, A. (2002). "Ulmaceae, in Wu, Z. & Raven, P. (eds)" (PDF). Flora of China. Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis, USA. 5. (Ulmaceae through Basellaceae)
  2. ^ Griffin, J.; et al. (2017). "Ten-Year Performance of the United States National Elm Trial" (PDF). Arboriculture & Urban Forestry. International Society of Arboriculture, Atlanta, US. 43(3):107–120.
  3. ^ a b "Accolade Elm - Ulmus x 'Accolade'". Cirrusimage.com. Retrieved 20 December 2018.
  4. ^ Iles, J. (2009). Forget your fear of the elms. Western University website
  5. ^ Ware, G. Morton Arb. Quarterly, 28(1): 1–5, 1992.
  6. ^ Giblin, C. P. & Gillman, J. H. (2006). Elms for the Twin Cities: A Guide for Selection and Maintenance. University of Minnesota.
  7. ^ McPherson, G. et al. (2008). National elm trial: Initial report from Northern California. Western Arborist, Fall 2009, 32–36.
  8. ^ Brady, C., Condra, J., & Potter, D. (2008) Resistance of Landscape-suitable Elm (Ulmus spp.) Cultivars to Japanese Beetle, Leaf Miners, and Gall Makers. 2008 Research Report, Nursery & Landscape Program, 15–16. University of Kentucky.
  9. ^ Shirazi, A. M. & Ware, G. H. (2004). Evaluation of New Elms from China for Cold Hardiness in Northern Latitudes. International Symposium on Asian Plant Diversity & Systematics 2004, Sakura, Japan.
  10. ^ Guries, R. P. & Smalley, E. B., (1986), Proc. Third Nat. Urban Forestry Conf., 214–218, 1986, Orlando, Florida.
  11. ^ "Thinking of ash alternatives? Don't forget about elms". MSU Extension. Retrieved 20 December 2018.
  12. ^ "National Elm Trial". 26 February 2008. Archived from the original on 26 February 2008. Retrieved 20 December 2018.
  13. ^ "The Dawes Arboretum - Newark, Ohio". 25 October 2007. Archived from the original on 25 October 2007. Retrieved 20 December 2018.
  14. ^ "Accolade". Archived from the original on 24 March 2012. Retrieved 20 December 2018.
  15. ^ "Photograph of autumn colouring of young 'Accolade' elms before Suzzallo Library: Arthur Lee Jacobson, 'Plant of the Month, 2008'". Arthurleej.com. Retrieved 20 December 2018.

External links[]

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