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

Related pages

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.