The American Elm

American Elm

Ulmus americana, generally known as the American Elm or, less commonly, as the White Elm or Water Elm, is a species native to eastern North America, occurring from Nova Scotia west to Alberta and Montana, and south to Florida and central Texas. The American elm is an extremely hardy tree that can...

 Ulmus americana cultivar 'Washington' is a tree of unknown derivation introduced by the U. S. National Park Service

National Park Service

The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...

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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 American Elm and a diploid species. However, in view of a study performed by the United States National Arboretum in 2004 http://www.elmpost.org/jeh905.pdf, this earlier supposition is likely to be erroneous; therefore, like the cultivar 'Jefferson' which was also once considered triploid, 'Washington' is probably tetraploid.

Pests and diseases

The tree is resistant to Dutch elm disease

Dutch elm disease

Dutch elm disease is a disease caused by a member of the sac fungi category, affecting elm trees which is spread by the elm bark beetle. Although believed to be originally native to Asia, the disease has been accidentally introduced into America and Europe, where it has devastated native...

, 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

Elm Yellows

Elm Yellows is a plant disease of elm trees that is spread by leafhoppers or by root grafts. Elm Yellows, also known as Elm Phloem Necrosis, is very aggressive, with no known cure. Elm Yellows occurs in the Eastern United States and southern Ontario in Canada. It is caused by phytoplasmas which...

. 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

Xanthogaleruca luteola

Xanthogaleruca luteola, commonly known as the Elm Leaf Beetle, is a serious pest of the elm. Indigenous to Europe, it was accidentally introduced to North America. Both the imagines and larvae feed on the emergent leaves of the elm...

http://www.bioone.org/doi/full/10.1603/0022-0493%282001%29094%5B0162%3AROTCEU%5D2.0.CO%3B2, and highly preferred for feeding by the Japanese Beetle Popillia japonica http://www.bioone.org/doi/full/10.1603/0022-0493%282001%29094%5B0445%3APOTCEU%5D2.0.CO%3B2 http://www.sunshinenursery.com/survey.htm in the USA.
U. americana is the most susceptible of all the elms to verticillium wilt

Verticillium wilt

Verticillium Wilt is a wilt disease of over 300 species of eudicot plants caused by one of two species of Verticillium fungus, V. dahliae and V. albo-atrum. Many economically important plants are susceptible including cotton, tomatoes, potatoes, eggplants, peppers and ornamentals, as well as others...

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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 USA.

North America

• Brooklyn Botanic Garden
  Brooklyn Botanic Garden
  Brooklyn Botanic Garden is a botanical garden in the borough of Brooklyn in New York City. Located near the Prospect Heights, Crown Heights, and Park Slope neighborhoods, the garden includes a number of specialty "gardens within the Garden," plant collections, and the Steinhardt Conservatory,...
  
   http://www.bbg.org/cgi/bgbase/search.cgi, New York
  New York
  New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
  
  . Acc. no. 850233.
• Smith College
  Smith College
  Smith College is a private, independent women's liberal arts college located in Northampton, Massachusetts. It is the largest member of the Seven Sisters...
  
  . Acc. no. 41703.

External links

• http://fletcher.ces.state.nc.us/programs/nursery/metria/metria11/warren/elm.htm Return of the Elm -the status of elms in the nursery industry in 2000. Warren, K., J. Frank Schmidt and Co.