Ulmus × hollandica 'Pioneer'

The hybrid elm cultivar Ulmus × hollandica 'Pioneer' is an American clone arising from the crossing of two European species, Wych Elm U. glabra (female parent) and Field Elm U. minor. Raised by the USDA station at Delaware, Ohio, in 1971, 'Pioneer' was released to commerce in 1983.

Ulmus × hollandica 'Pioneer'
'Pioneer', Netherlands
Hybrid parentageU. glabra × U. minor
Cultivar'Pioneer'
OriginUS

Description

'Pioneer' is a fast-growing tree distinguished by a dense, globular crown, which as it matures becomes more broad than tall, like its U. glabra parent,[1] and casting a heavy shade. The leaves are deep green, and similar in shape to the Wych Elm,[2] colouring yellow and red in the fall.[3] The perfect, apetalous wind-pollinated flowers appear in early March.

Pests and diseases

The tree's resistance to Dutch elm disease, rated 4 out of 5,[4] is somewhat less than more recent American hybrids, and for this reason the tree was omitted from the elm trials in eastern Arizona conducted by the Northern Arizona University. 'Pioneer' is also severely damaged by the Elm Leaf Beetle Xanthogaleruca luteola,[5] sustaining more foliar damage (50%) than any other cultivar in an assessment conducted as part of the National Elm Trial at U C Davis,[6] and Japanese Beetle.[7] Tolerance of Elm Yellows in the United States was also found to be poor.[8]

The tree's foliage was adjudged "resistant" to Black Spot by the Plant Diagnostic Clinic of the University of Missouri .

Cultivation

Considered "quite hardy in Saint Paul", and "definitely a good selection for the Twin Cities (St. Paul and Minnesota) urban forest" although very different in appearance to the American Elm.[9] 'Pioneer' has had a very limited introduction to Europe,[10] featuring in street tree trials in several Dutch cities in the late 1990s. The tree has reputedly been planted in Preston Park, Brighton, and along Tisbury Road, Hove, but does not feature in the NCCPG National Elm Collection held there.[11]

  • Elm cultivars, Netherlands; 'Pioneer' 3rd from left
  • 'Pioneer' in Toronto (May 2016)

Accessions

North America

Europe

Nurseries

North America

Europe
  • Noordplant , Glimmen, Netherlands.
  • Van Den Berk (UK) Ltd., , London, UK
  • Westerveld Boomkwekerij B.V., Opheusden, Netherlands.

References
  1. Arthur Lee Jacobson, 'Plant of the Month, 2008' (arthurleej.com/p-o-m-Oct08.html). Photographs of 'Pioneer' elm: www.ca.uky.edu and plants.bachmanslandscaping.com
  2. Santamour, J., Frank, S. & Bentz, S. (1995). Updated checklist of elm (Ulmus) cultivars for use in North America. Journal of Arboriculture, 21:3 (May 1995), 121–131. International Society of Arboriculture, Champaign, Illinois, US.
  3. Photograph of autumn colouring of young 'Pioneer' elms, University of Washington campus: Arthur Lee Jacobson, 'Plant of the Month, 2008'
  4. Heybroek, H. M., Goudzwaard, L, Kaljee, H. (2009). Iep of olm, karakterboom van de Lage Landen (:Elm, a tree with character of the Low Countries). KNNV, Uitgeverij. ISBN 9789050112819
  5. "Elm Leaf Beetle Survey". Archived from the original on 2011-07-19. Retrieved 17 July 2017.
  6. McPherson, G. et al. (2008). National elm trial: Initial report from Northern California. Western Arborist, Fall 2009, pp 32-36.
  7. 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.
  8. Sinclair, W. A., Townsend, A. M., Griffiths, H. M., & Whitlow, T. H. (2000). Responses of six Eurasian Ulmus cultivars to a North American elm yellows phytoplasma. Plant disease, Vol. 84, No.12, 1266–1270. American Phytopathological Society, St. Paul, MN
  9. Giblin, C. P. & Gillman, J. H. (2006). Elms for the Twin Cities: A Guide for Selection and Maintenance. University of Minnesota.
  10. Burdekin, D.A.; Rushforth, K.D. (November 1996). Revised by J.F. Webber. "Elms resistant to Dutch elm disease" (PDF). Arboriculture Research Note. Alice Holt Lodge, Farnham: Arboricultural Advisory & Information Service. 2/96: 1–9. ISSN 1362-5128. Retrieved 26 October 2017.
  11. "List of plants in the {elm} collection". Brighton & Hove City Council. Retrieved 23 September 2016.
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