Ulmus americana 'Valley Forge'

Infobox Cultivar | name = "Ulmus americana"
cultivar = 'Valley Forge'
origin = Maryland Agricultural Research Service, USAThe American Elm "Ulmus americana" cultivar 'Valley Forge' was raised by the Maryland Agricultural Research Service and released to wholesale nurseries by the U. S. National Arboretum in 1995.

Description

Michael A. Dirr, Professor of Horticulture at the University of Georgia described the tree's form as "floppy" [http://www.greenbeam.com/rs/nm.pdfs/16338_012.pdf] .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included in 10-year trials at Atherton, California, to evaluate replacements for Californian elms lost to disease were withdrawn after a combination of rapid growth and poor structure condemned the trees as "likely to require more maintenance than most municipalities would find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" Costello, L. R. (2004). A 10-year evaluation of the performance of four elm cultivars in California, U. S. "Journal of Arboriculture", March 2004. [http://www.findarticles.com/p/articles/mi_qa4107/is_200403/ai_n9387070/print] ] . However, these verdicts may reflect in large measure the fact that they were grown in warm climates but with minimal weed competition. 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 Giblin, C. P. & Gillman, J. H. (2006). "Elms for the Twin Cities: A Guide for Selection and Maintenance." University of Minnesota.] . '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. Moreover, where grown in the countryside, competing vegetation tends to keep excessively vigorous growth in check [http://www.elmpost.org/elmpics.htm] .

Pests and diseases

'Valley Forge' is the most Dutch elm disease-resistant of all the American Elms. However, although also resistant to the elm leaf beetle "Xanthogaleruca luteola" [http://commons.wikimedia.org/wiki/Xanthogaleruca_luteola] , like all other American Elms it is susceptible to Elm Yellows Townsend, A. M., Bentz, S. E., and Douglass L. W. (2005). [http://www.elmpost.org/19elms.pdf Evaluation of 19 American Elm Clones for Tolerance to Dutch Elm Disease] . "Journal of Environmental Horticulture", March 2005, Horticultural Research Institute, Washington, D.C.] .

Cultivation

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 [http://treehealth.agsci.colostate.edu/research/nationalelmtrial/NET_Cultivars.htm] coordinated by Colorado State University. The tree is not known to have been introduced to Europe or Australasia.

Etymology

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

Accessions

;North America
*Arnold Arboretum, acc. no. 180-2003.
*Bartlett Tree Experts [http://www.bartlett.com/,] acc. nos. 2001-258, 2001-259, 2001-486, 2001-491, 2003-1010.
*Brenton Arboretum, Dallas Center, Iowa. No details available.
*Dawes Arboretum [http://www.dawesarb.org/collectionsgardens/plant-search.asp] , Newark, Ohio. 2 trees, no acc. details available.
*Holden Arboretum, acc. nos. 2002-76, 2004-38, 2004-47.
*Scott Arboretum, acc. no. 98-110
*Smith College, acc. no. 36205.

Nurseries

;North America
*Klyn Nurseries [http://www.klynnurseries.com/history.htm] , Perry, Ohio.
*The Botany Shop Garden Center [http://www.botanyshop.com/ValleyForge.htm] , Missouri

References

External links

*http://www.extension.iastate.edu/Publications/SUL4.pdf Summary, inc. photographs, of elm cultivars resistant to Dutch elm disease available in the USA.
* [http://www.elmpost.org Saving the American Elm, by Bruce Carley]
* [http://www.elmpost.org/vforge.htm Photograph of the 20-year-old form of the Valley Forge elm]
*http://www.sunshinenursery.com/elms.htm Review of current elm selections in the USA.