The original native American Elm of the turn of the 20th century was massive, long-lived, tough, easy to grow, adaptable and displayed a wonderful vase-like silhouette that was second to none as a street tree. The modern clones of the American Elm and a number of the hybrids are expected to offer the exact same benefits. The oldest clone is only 18 years old, so we have a bit of a wait to see how old the new clones can get.
American Elms reach a mature height of 40 to 70 feet with a spread of 2/3 to 3/4 their height.. Elms are deciduous. The leaves, up to six inches long, are toothed along the edges, have uneven bases and grow alternately along the stem. American Elm foliage turns a rich yellow or gold in fall and stays on the tree late in the season. The flowers appear in early spring and are insignificant giving just a tinge of reddish color to the tree because the leaves have not yet appeared. Soon after a heavy crop of papery, disc-winged seeds about 1/3 inch long develops. The American Elm is the state tree for Massachusetts and for North Dakota
American Elm Choices
All of these trees exhibit excellent resistance to Dutch Elm Disease. They are not immune, but if attacked they are able to localize the effects and successfully recover from the disease.
Frontier Elm shows high resistance not only to Dutch Elm Disease, but is resistant to elm leaf bgheetles, and elm yellows disease. In autumn the pyramidal crown of Frontier turns reddish-purple. Prospector Elm is a hybrid with the same resistance to problems as Frontier , this vase-shaped crown turns yellow in fall. The Frontier Elm is considered in 2008 to be the toughest, and most reliable Elm for the urban or suburban environment.
American Liberty Elm is a fast growing clone and tolerant to many urban stresses, such as salt injury, soil compaction, and drought damage. It has the same vase shape as the original native species. It develops a vigorous upright main trunk in youth with older branches tending to become more horizontal at maturity. The Liberty Elm is distributed by the Elm Research Institute in Harrisville, New Hampshire, a non-profit group dedicated to re-introducing the American Elm to America. They can be reached at http - //www.libertyelm.com/.
Princeton Elm is a clone available from the Princeton Nurseries in New Jersey. Valley Forge Elm is a clone released by the National Arboretum, this tree has an upright, arching broadly V-shaped branch structure with a full dense leaf canopy.
New Harmony Elm is another clone also released from the National Arboretum, it has a broadly V-shaped crown. The main trunk divides nearly 30 feet from the ground into a few erect branches. Leaves are 4 inches long a 5 ½ inches wide with yellow fall color. Zones 4 to 7.