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Ulmus americana, generally known as the American elm or, less commonly, as the white elm or water elm, [a] is a species of elm native to eastern North America. The trees can live for several hundred years.
The tree can grow to greater than 30 m in height, and is distinguished by its dense, symmetrical, upright form and dark green foliage, ultimately forming a broad umbrella crown. Crotch angles can be acute, with considerable bark inclusion which can later lead to branch breakages. The leaves are less than 16 cm long by 8 cm broad.
Officially it is a specimen of Ulmus americana, but is unusual because it grows sideways, making it a "tabletop" elm tree. The tree was planted in 1927, and currently its several branches are supported by specialized braces to allow movement and growth. Every fall seven dump truck loads are required to remove all the leaves.
The American elm cultivar Ulmus americana 'New Harmony' was raised by the Maryland Agricultural Research Service and released by the United States National Arboretum in 1995, along with 'Valley Forge'. 'New Harmony' proved the most successful U. americana cultivar in the US National Elm Trial, averaging a survival rate of 85.5% overall. [1]
Ulmus americana var. floridana, the Florida elm, first described as Ulmus floridana by Alvan Wentworth Chapman in the 1860s, is smaller than the type, and occurs naturally in north and central Florida south to Lake Okeechobee.
The American Elm cultivar Ulmus americana 'Jefferson' was cloned from a tree growing near a path in front of the Freer Gallery of Art, close to the Smithsonian Institution Building ("The Castle") on the National Mall in Washington, D.C. [1] The United States National Park Service, which had planted the tree during the 1930s, cloned it in 1993 after screening tests showed that it possessed an ...
The leaves differ from those of the common form," wrote Rehder (1922), "in being rather broad, measuring up to 7.5 cm. in width, very sharply and deeply doubly serrate, scabrous above, pilose on the veins and veinlets beneath and very unequal at the base; the petioles are very short, not exceeding 3 mm. in length; the young branchlets are ...
[2] [4] Its leaves are similar in shape and texture to those of the parent species, but slightly smaller. Arnold Arboretum, however, report leaves 3 to 6 in. long and 2 to 4 in. wide. [5] The bark remains smooth for longer than usual in the species and its fissures are less deep, while the trunk lacks the marked buttressing of the species. [1]