The American elm cultivar Ulmus americana 'New Harmony' was raised by the Maryland Agricultural Research Service and released by the United States National Arboretum in 1995, along with 'Valley Forge'. 'New Harmony' proved the most successful U. americana cultivar in the US National Elm Trial, averaging a survival rate of 85.5% overall.
Description 'New Harmony' is considered by some to have a more desirable form than 'Valley Forge' as it grows vertically on its own with a minimum of early training. The original parent tree (located on a roadside in Ohio) is already over 20 m high, with a slightly greater crown spread. The bole divides into several erect branches about 10 m above the ground terminating in slender, pendulous branchlets.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.
Growth is rapid, young trees gaining in height by almost 1.7 m per annum in trials at U C Davis, although d.b.h. increase remained a modest 1.8 cm.McPherson, G. et al. (2008). National elm trial: Initial report from Northern California. Western Arborist, Fall 2009, 32–36.
Pests and diseases Although resistant to Dutch elm disease and elm leaf beetle Xanthogaleruca luteola, like most other American elm cultivars 'New Harmony' is susceptible to elm yellows and Japanese beetle Popillia japonica.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. In the trials at U C Davis, the trees remained free of leaf curling aphids (Eriosoma), unlike its U. americana stablemates 'Valley Forge' and 'Princeton'.
Cultivation 'New Harmony' is currently being evaluated in the National Elm Trial coordinated by Colorado State University. Five trees stand (2026) before the Student Experience Center, Oregon State University, Corvallis.Oregon State University Landscape Plants, U. Americana; landscapeplants.oregonstate.edu The tree was introduced to the UK and the Netherlands in 2010.M.Tijdgat, 'De Nederlandse Planten Collecties', Ulmus; plantencollecties.nl
Etymology The tree is named for the Indiana town renowned for its social innovations in the 19th century.
Accessions North America Bartlett Tree Experts, US. Acc. nos. 2001-233, 2001-446. Brenton Arboretum, Dallas Center, Iowa, US. No details available. Longwood Gardens, US. Acc. nos. 2000-0361, 2002-0412, 2004–0674. Morton Arboretum, Illinois, US. Acc. no. 124-2008. U S National Arboretum , Washington, D.C., US. Acc. no. 29003. Europe Grange Farm Arboretum, Sutton St. James, Spalding, Lincolnshire, UK. Whips planted 2011. Acc. no. 1055. Netherlands Plant Collection, Ulmus: Gemeentehuis, Rading 1, Loosdrecht, gemeente Wijdemeren, planted 2016.Netherlands Plant Collection: Iepen, Ulmus
References
External links http://www.elmpost.org/2003-08.htm Photograph of New Harmony elms in their original test plot, showing their form of growth. http://www.extension.iastate.edu/Publications/SUL4.pdf Summary, including photographs, of elm cultivars resistant to Dutch elm disease available in the United States. http://www.sunshinenursery.com/elms.htm Review of current elm selections in the United States. https://web.archive.org/web/20061205022500/http://www.ces.ncsu.edu/fletcher/programs/nursery/metria/metria11/warren/elm.htm Return of the Elm -the status of elms in the nursery industry in 2000. Warren, K., J. Frank Schmidt and Co.