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The American Elm cultivar Ulmus americana 'St. Croix' is a recent (2008) selection cloned from a large tree growing on a farm near Afton, Minnesota, [1] which has displayed a high resistance to Dutch elm disease (DED). [2] A U S patent, PP 20097, was granted in 2009.
American elm is a vase-shaped, medium to large, deciduous tree. [4] 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 'Valley Forge' was raised by the Agricultural Research Service in Maryland. The tree was released to wholesale nurseries without patent restrictions by the U. S. National Arboretum in 1995 after proving to have a high resistance to Dutch elm disease. 'Valley Forge' proved only moderately successful in ...
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 American elm is a deciduous tree which, under ideal conditions, can grow to heights of 21 to 35 meters (69 to 115 feet). [3] The trunk may have a diameter at breast height (dbh) of more than 1.2 m (4 ft), supporting a high, spreading umbrella-like canopy.
The Chinese Elm cultivar Ulmus parvifolia 'Drake' was marketed by the Monrovia Nursery of Azusa, California, first appearing in their 1952–1953 catalogue. [ 1 ] Description
Ulmus 'Patriot' is a hybrid cultivar raised by the United States National Arboretum in 1980. Derived from a crossing of the American hybrid 'Urban' (female parent) with the Wilson's Elm (now treated as Japanese Elm U. davidiana var. japonica) cultivar 'Prospector', 'Patriot' was released to commerce, free of patent restrictions, in 1993.
The American elm cultivar Ulmus americana 'American Liberty' is in fact a group of six genetically distinct cultivars under a single name, although they are superficially similar. [1] The Liberty elm is reportedly suitable for street planting, being tolerant of de-icing salts and air pollution.