page_title: Ulmus americana
section_title: Central Park
hierarchical_section_title: Ulmus americana / Landscaped parks / Central Park
caption_attribution_description: English: Central Park-The Mall
context_page_description: 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, naturally 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 withstand winter temperatures as low as −42 °C. Trees in areas unaffected by Dutch elm disease can live for several hundred years. A prime example of the species was the Sauble Elm, which grew beside the banks of the Sauble River in Ontario, Canada, to a height of 43 m, with a d.b.h of 196 cm before succumbing to DED; when it was felled in 1968, a tree-ring count established that it had germinated in 1701.
  For over 80 years, U. americana had been identified as a tetraploid, i.e. having double the usual number of chromosomes, making it unique within the genus. However, a study published in 2011 by the Agricultural Research Service of the USDA revealed that about 20% of wild American elms are diploid and may even constitute another species.
context_section_description: New York City's Central Park is home to approximately 1,200 American elms, which constitute over half of all trees in the park. The oldest of these elms were planted during the 1860s by Frederick Law Olmsted, making them among the oldest stands of American elms in the world. The trees are particularly noteworthy along the Mall and Literary Walk, where four lines of American elms stretch over the walkway forming a cathedral-like covering. A part of New York City's urban ecology, the elms improve air and water quality, reduce erosion and flooding, and decrease air temperatures during warm days.
  While the stand is still vulnerable to DED, in the 1980s the Central Park Conservancy undertook aggressive countermeasures such as heavy pruning and removal of extensively diseased trees. These efforts have largely been successful in saving the majority of the trees, although several are still lost each year. Younger American elms that have been planted in Central Park since the outbreak are of the DED-resistant 'Princeton' and 'Valley Forge' cultivars.
caption: American elms along The Mall and Literary Walk, Central Park (2013)
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