| Ulmus americana | |
|---|---|
| Details | |
| Cultivar | 'Delaware' |
| Origin | USDA, Morristown, New Jersey, USA |
The American Elm Ulmus americana cultivar 'Delaware' was originally selected (as tree number 218) from 35,000 seedlings inoculated with the Dutch elm disease fungus in USDA trials at Morristown, New Jersey.
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The tree has a relatively low stature and "undesirable" branching habit.[1][2]
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.
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'. 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.
NB 'Delaware I' is the original name given to the hybrid 'Urban' before its commercial release.