Ulmus americana 'Valley Forge'

From Wikipedia, the free encyclopedia

Ulmus americana
Cultivar
'Valley Forge'
Origin
Maryland Agricultural Research Service, USA

The American Elm Ulmus americana cultivar 'Valley Forge' is the most Dutch elm disease-resistant of all the American Elms. Raised by the Maryland Agricultural Research Service, it was released to wholesale nurseries by the U. S. National Arboretum in 1995. Although also resistant to elm leaf beetle, like all other American Elms 'Valley Forge' is susceptible to elm yellows [1]. All examples included in 10-year trials at Atherton, California, to evaluate replacements for Californian elms lost to disease, were withdrawn after a combination of rapid growth and poor structure condemned the trees as likely to require more maintenance than most municipalities would find acceptable [2]. However, the performance of the trees in that study may reflect in large measure the fact that they were grown in a southern climate with minimal weed competition. Likewise, trees raised in the nursery of the University of Minnesota proved very difficult to manage, but "settled down" as they matured, adopting a more manageable form and habit [3]. Michael A. Dirr, Professor of Horticulture at the University of Georgia described the tree's form as "floppy" [2].

'Valley Forge' seems to develop far fewer structural problems in temperate climates further north, where the rate of growth in any given season is much more moderate, as well as in meadows, where competing vegetation tends to keep excessively vigorous growth in check [3]. Although this cultivar requires regular attention to training and pruning in its early years, such training by some accounts is easy enough to accomplish by those who are committed. The tree is currently being evaluated in the National Elm Trial [4] coordinated by Colorado State University.

The tree is not known to have been introduced to Europe or Australasia.

Contents

[edit] Arboreta etc. accessions

North America

[edit] Nurseries

North America
  • Klyn Nurseries [7], Perry, Ohio.
  • The Botany Shop Garden Center [8], Missouri

[edit] Etymology

'Valley Forge' was named for the site near Philadelphia where Washington's forces endured the winter of 1777 during the War of Independence.

[edit] References

  1. ^ Townsend, A. M., Bentz, S. E., and Douglass L. W. (2005). Evaluation of 19 American Elm Clones for Tolerance to Dutch Elm Disease. Journal of Environmental Horticulture, March 2005, Horticultural Research Institute, Washington, D.C.
  2. ^ Costello, L. R. (2004). A 10 -year evaluation of the performance of four elm cultivars in California, U. S. Journal of Arboriculture, March 2004. [1]
  3. ^ Giblin, C. P. & Gillman, J. H. (2006). Elms for the Twin Cities: A Guide for Selection and Maintenance. University of Minnesota.

[edit] External links