'New Harmony' Elm

New Harmony Elm (Ulmus americana 'New Harmony')

'New Harmony' is a pure American elm cultivar released by the USDA National Arboretum in 1995 alongside 'Valley Forge'. It combines high DED resistance with a somewhat tighter, more uniform crown than its sister release, making it particularly useful in spaces that cannot accommodate the broad spread of the classic American vase.

Origin

'New Harmony' is a pure Ulmus americana selection from the USDA National Arboretum's American elm breeding program led by Alden Townsend. Like 'Valley Forge', it descends from a small set of survivor trees identified during decades of screening across hundreds of pure American elm selections. Both 'New Harmony' and 'Valley Forge' were advanced through repeated inoculation trials with virulent Ophiostoma novo-ulmi strains before commercial release.

The cultivar was named after the historic community of New Harmony, Indiana.

Identification

Form: Vase-shaped but more compact than 'Valley Forge' — narrower crown spread with somewhat more symmetric branching

Mature size: 60–70 feet tall, 40–50 foot crown spread (narrower than 'Valley Forge')

Leaves: Standard Ulmus americana foliage — 3–5 inch oval, double-serrated, asymmetric base

Bark: Light gray, deeply furrowed at maturity

Growth rate: Fast

Hardiness and adaptability

USDA hardiness zones: 4–9

Site preferences: Adaptable to most soils; tolerates urban conditions

Stress tolerance: Drought-tolerant once established

Dutch Elm Disease resistance

'New Harmony' shows high resistance to DED, comparable to 'Valley Forge'. In USDA inoculation trials the cultivar demonstrated minimal vascular discoloration and high survival following challenge with virulent Ophiostoma novo-ulmi. Townsend et al. (2005) reported survival rates and crown retention statistically similar to 'Valley Forge'.

Field performance since release has supported the trial results, with 'New Harmony' generally rated among the top three or four most resistant pure American elm cultivars in commercial production.

Landscape uses

Street trees on narrower right-of-ways where 'Valley Forge's full vase spread is impractical

Urban canopy restoration plantings

Mixed plantings with 'Valley Forge' and other resistant cultivars to maintain diversity

Park and residential plantings

Limitations

Crown architecture develops over 15–25 years; young trees can appear irregular

Susceptible to elm yellows (a phytoplasma disease distinct from DED)

Requires structural pruning during early establishment

Sometimes confused with 'Valley Forge' in trade; verify cultivar identity at purchase

Similar cultivars

'Valley Forge' — USDA companion release, broader form

'Princeton' — older selection with moderate resistance

'Jefferson' — hexaploid American elm with high resistance

Related pages

What Cultivars Are Resistant to Dutch Elm Disease?

Disease-Resistant Varieties Guide

American Elm (Ulmus americana)

References

Townsend, A. M., Bentz, S. E., & Douglass, L. W. (2005). "Evaluation of 19 American elm clones for tolerance to Dutch elm disease." Journal of Environmental Horticulture, 23(1), 21–24.

Townsend, A. M. (1995). "'Valley Forge' and 'New Harmony' elms (US National Arboretum release)." USDA-ARS plant introduction record.

Griffin, J. J., Jacobi, W. R., McPherson, E. G., et al. (2017). "Ten-year performance of the United States National Elm Trial." Arboriculture & Urban Forestry, 43(3), 107–120.