Ulmus × hollandica 'Pioneer'

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Ulmus × hollandica
RN Ulmus hollandica Pioneer.JPG
'Pioneer', Netherlands. Photo: Ronnie Nijboer
Hybrid parentage U. glabra × U. minor
Cultivar 'Pioneer'
Origin USA

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


RN Ulmus hollandica Pioneer leaves.jpg

'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[edit]

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 [2] in eastern Arizona conducted by the Northern Arizona University. 'Pioneer' is also severely damaged by the Elm Leaf Beetle Xanthogaleruca luteola [3], sustaining more foliar damage (50%) than any other cultivar in an assessment conducted as part of the National Elm Trial at U C Davis.,[5] and Japanese Beetle.[6] Tolerance of Elm Yellows in the USA was also found to be poor. [7]

The tree's foliage was adjudged "resistant" to Black Spot by the Plant Diagnostic Clinic of the University of Missouri [4].


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.[8] 'Pioneer' has had a very limited introduction to Europe,[9] featuring in street tree trials in several Dutch cities in the late 1990s.


North America[edit]



North America[edit]



  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, USA.
  3. ^ Photograph of autumn colouring of young 'Pioneer' elms, University of Washington campus: Arthur Lee Jacobson, 'Plant of the Month, 2008' [1]
  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. ^ McPherson, G. et al. (2008). National elm trial: Initial report from Northern California. Western Arborist, Fall 2009, pp 32-36.
  6. ^ 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, pp 15, 16. University of Kentucky.
  7. ^ 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
  8. ^ Giblin, C. P. & Gillman, J. H. (2006). Elms for the Twin Cities: A Guide for Selection and Maintenance. University of Minnesota.
  9. ^ Burdekin, D. A. & Rushforth, K. D. (Revised by Webber J. F. 1996). Elms resistant to Dutch elm disease. Arboricultural Research Note 2/96. Arboricultural Advisory and Information Service, Alice Holt, Farnham, UK.

External links[edit]