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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 American elm cultivar Ulmus americana 'Lewis & Clark' (trade name Prairie Expedition) is a development from the North Dakota State University (NDSU) Research Foundation breeding programme, released in 2004 to commemorate the 200th anniversary of the eponymous expedition. [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 tree is highly resistant to Dutch elm disease. [1] No other specific information is available, but the species as a whole is highly susceptible to Elm Yellows; it is also moderately preferred for feeding and reproduction by the adult Elm Leaf Beetle Xanthogaleruca luteola, [3] and highly preferred for feeding by the Japanese Beetle Popillia japonica [4] [5] in the United States.
A clone cultivated in China as Ulmus americana 'Pendula', top-grafted on Ulmus pumila stock, is neither Ulmus americana nor Scampston elm (formerly mis-named Ulmus americana 'Pendula'), but, in the case of the majority of photographs on the Plant Photo Bank of China, a weeping form of U. glabra Huds., probably 'Camperdownii'. [18] [19]
The American elm cultivar Ulmus americana 'Aurea' was cloned from a tree discovered by F. L. Temple in Vermont at the end of the 19th century. [1] [2] Description
As implied by its name, the tree has a fastigiate, columnar form, [4] of almost equal width from the base to a top which is rather flat in appearance. [2] " 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 ...