US National Arboretum


Tolerant American Elms - 'Valley Forge' & 'New Harmony' 'Valley Forge' and 'New Harmony'

The U.S. National Arboretum is pleased to announce the release of two new Dutch elm disease tolerant American elms, 'Valley Forge' and 'New Harmony'. Over the past 50 years, millions of stately elms shading the streets of the American landscape have been lost to Dutch elm disease (DED). Selected after 20 years of research, both 'Valley Forge' and 'New Harmony' have good levels of disease tolerance, although neither is immune to DED. Both cultivars possess the "classic" American elm shape and the tolerance to air pollution and poor soil conditions of the species. 'Valley Forge' and 'New Harmony' present a new opportunity to plant an old American favorite. Plant history. Plant a disease-tolerant American elm!

Recognition: 'Valley Forge' planted on the grounds of the U.S. Capitol, June 6, 1996.

Picture of American Elm 'Valley Forge' Picture of American Elm 'New Harmony'

Tolerant American Elms - 'Valley Forge' & 'New Harmony' - page 2 'Valley Forge' and 'New Harmony' American Elms

Botanical Name: Ulmus americana 'Valley Forge'
(NA 57842; PI 590997)
Ulmus americana 'New Harmony'
(NA 57844; PI 590998)
Family: Ulmaceae
Hardiness: U.S.D.A Zones 5-10, 'New Harmony'
U.S.D.A Zones (4)5-9, 'Valley Forge'
Development: Both cultivars are seedling selections made in Delaware, OH for DED tolerance by A.M. Townsend and L.R. Schreiber. DED is caused by a fungus introduced by the elm bark beetle into healthy elms from dead and dying trees and may spread from tree to tree through root grafts. Of thousands of American elms screened by inoculation with aggressive and non-aggressive strains of the DED fungus, 'Valley Forge' was the most tolerant, with 'New Harmony' a close second. Neither selection is immune to DED. Released 1995.
Significance: 'Valley Forge' and 'New Harmony' are the first "commercially" available DED-tolerant American elms. High levels of DED tolerance and superior horticultural characteristics including tolerance to air pollution, drought and poor soil conditions make these cultivars ideal candidates for the urban landscape.
Description: Height and width: 'Valley Forge': 26 feet tall, 30 foot crown spread at 12 years old. 'New Harmony': 68 feet tall, 72 foot crown spread at maturity.
Growth rate: Once established, as much as 3 feet per year.
Habit: Classic American elm form. 'Valley Forge': upright, arching, broadly vase-shaped with full, dense leaf canopy. 'New Harmony': broadly V-shaped crown with limbs terminating in numerous slender, often drooping, branches.
Foliage: Leaves 4.2-4.6 inches long, 2.5-2.9 inches wide; yellow fall color.
Culture: Adaptable to a wide variety of soil conditions. American elms tolerate deicing salts, drought, poor soil conditions, air pollution and range of pH¹s. Prune to establish central leader. Plant with other species and elm cultivars to prevent spread of disease.
Propagation: Roots from softwood cuttings under mist, 3000 ppm - 8000 ppm IBA, in 3-6 weeks. Rooted cuttings that break bud will transplant successfully in the current year. Provide overwinter protection.
Landscape Use: Urban and suburban settings, large recreation and industrial parks.
Distribution: Distributed to wholesale nurseries in 1994-1996. Limited wholesale and mail order availablity as of 2004.

U.S. National Arboretum Plant Introduction
Floral and Nursery Plants Research Unit
U.S. National Arboretum, U.S. Department of Agriculture, Agricultural Research Service, 3501 New York Ave., N.E., Washington, DC 20002

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