Elm trees are members of the ulmaceae family, a group of trees distributed predominantly in northern, temperate regions. Elm trees were once significant features of the American landscape. However, Dutch elm disease, introduced into the United States in the 1930s, destroyed vast portions of native elm tree populations, both wild and those planted in urban settings. Non-native elms are less prone to Dutch elm disease, and varieties of American elms resistant to the disease are being developed.
Elms are deciduous trees of various size form depending on the species. Species such as the American elm (Ulmus americana) reach up to 120 feet tall, with arching limbs and a vase-like, symmetrical crown of foliage. The dwarf elm (Ulmus pumila) is a small tree or shrub reaching 25 feet tall. Elm leaves are simple, with rounded bases, tapering tips and serrated margins.
The American elm is found throughout the United States. It has ash-gray bark forming deep diamond-shaped grooves. American elm leaves are 4 to 6 inches long and 2 to 3 inches wide. American elms are drought-tolerant but prone to pests when water-stressed. These trees prefer growing in full sun to partial shade locations and are cold-hardy to USDA zone 2.
Winged elms (Ulmus alata) become vase-shaped with maturity and reach up to 60 feet tall, with a 30 foot spread. Winged elm leaves are 2 inches long and their stems have thin, corky, winglike outgrowths on either side. These elms prefer full sun or partial shade and well-drained soils. Winged elms are hardy to USDA Zone 5.
The Chinese elm (Ulmus parviflora) is a spreading, open-canopied, Asian elm tree with a slightly weeping form. It has 3 inch, shiny, dark-green, leathery leaves and grow up to 80 feet tall, rapidly. Chinese elms prefer full sun and various soils and are hardy to USDA Zone 5.
Use the large species as shade trees, for street plantings or as specimen trees in the landscape. Use of non-native species, or disease-resistant American species, is recommended because of Dutch elm disease. Other uses of elms include wood for making furniture, crates and firewood.
Elms grow best in moist, nutrient-rich, well-drained soils and sunny locations. Avoid construction and other mechanical damage of elm roots to avoid introducing disease-carrying pests into the root system. Avoid mass plantings of native American elm species to reduce the chance of spreading disease. Grow Asiatic elms when possible or locate disease-resistant American cultivars such as American Liberty, Valley Forge and New Freedom.
Besides Dutch elm disease, elm tree pests include borers, black leaf spot, branch cankers, cankerworms and aphids. Deer chew stems and twigs, causing damage on young trees. County extension offices provide helpful information regarding pest and disease identification and control.