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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 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 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.
Rows of American elm trees line a path south of the Lincoln Memorial Reflecting Pool on the National Mall in Washington, DC (November 11, 2006) Several rows of American elm trees that the National Park Service (NPS) first planted during the 1930s line much of the 1.9-mile-length (3 km) of the National Mall in Washington, DC. DED first appeared ...
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]
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 cultivar Ulmus americana 'Moline' was cloned from a wild seedling transplanted to Moline, Illinois, from nearby Rock River Valley in 1903 and propagated from 1916 by the Klehm Nurseries, Arlington Heights, Illinois. [1] [2] [3]
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.