Ulmus americana 'Delaware'

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The American Elm cultivar Ulmus americana 'Delaware' was originally selected (as tree number 218, a c.1940 seedling from North Dakota) from 35,000 seedlings inoculated with the Dutch elm disease fungus in USDA trials at Morristown, New Jersey.[1]

Ulmus americana 'Delaware'
Delaware Elm, USDA Washington
SpeciesUlmus americana
Cultivar'Delaware'
OriginUSDA, Morristown, New Jersey, US

Description

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'Delaware' bark

The tree has a relatively low stature and "undesirable" branching habit.[1][2]

Pests and diseases

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Further disease-resistance trials were conducted by both the USDA and the United States National Arboretum which confirmed the clone had a fair level of resistance to Dutch elm disease. 'Delaware' is susceptible to Elm Yellows, but resistant to the Elm Leaf Beetle Xanthogaleruca luteola.

Cultivation

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The original tree, which had been moved to the USDA National Arboretum, Washington, D. C. in 1948, died from unknown causes (probably elm yellows, by some accounts) in 1980, but a clone survives at the Denver Botanic Gardens, as 'Delaware II'. Seven specimens stand in the National Mall area, Washington D.C.[3][4] [5] Although propagated for further trials, the tree was never commercially released owing to its poor shape. 'Delaware' is not known to have been introduced to Europe or Australasia.

Synonymy

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  • 'Delaware II'.

NB 'Delaware I' is the original name given to the hybrid 'Urban' before its commercial release.

Accessions

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North America

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References

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  1. ^ a b Santamour, Frank S.; Bentz, Susan E. (May 1995). "Updated Checklist of Elm (Ulmus) Cultivars for use in North America". Journal of Arboriculture. 21 (3): 122–131. Retrieved 20 June 2016.
  2. ^ 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.
  3. ^ 'Delaware', Smithsonian Gardens, si.gardenexplorer.org
  4. ^ 'Delaware' before pruning, National Museum of Natural History, Constitution Avenue NW, Washington DC - Google Maps, March 2011, access date: 18 October 2022
  5. ^ Pruned 'Delaware', National Museum of Natural History, Constitution Avenue NW, Washington DC - Google Maps, August 2022, access date: 17 October 2022