Cultivar 'Washington' | Origin USA | |
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The American Elm cultivar Ulmus americana 'Washington' is a tree of unknown derivation introduced by the U. S. National Park Service.
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Description
The tree has been described as possibly having triploid chromosome levels (unusual for an American Elm), suggesting it may be a hybrid between the tetraploid and rarer diploid forms of American Elm, like the cultivar 'Jefferson'.
Pests and diseases
The tree is resistant to Dutch elm disease, but less so than other recent American Elm cultivars such as 'Valley Forge'. Like all other American Elm cultivars, it is also susceptible to Elm Yellows. No other specific information available, but the species generally is also moderately preferred for feeding and reproduction by the adult Elm Leaf Beetle Xanthogaleruca luteola [1], and highly preferred for feeding by the Japanese Beetle Popillia japonica [2] [3] in the United States. U. americana is the most susceptible of all the elms to verticillium wilt.
Cultivation
Neither 'Washington' nor 'Jefferson' has been widely tested beyond Washington D.C.. The tree is not known to be in commerce, and is not known to be in cultivation beyond the United States.