Since the beetle-carried fungus Dutch elm disease was first introduced into North America in the 1930s, American elms (Ulmus americana) were killed in innumerable amounts. Finding disease-resistant clones of elms became a priority in order to re-vegetate streetscapes and lawns with one of the most beautiful native deciduous trees. Cultivar Liberty was selected in the 1980s and planted. It is not fully resistant to the disease but often grows to mature size without detriment.
The American Liberty elm was developed from controlled pollinations of native elm trees made in 1968 and 1970 between trees showing superior resistance to Dutch elm disease. It is not a hybrid, but the result of a seed containing genes, making it more resilient to the disease. It is usually called a 'clone'.
Liberty elm is fast-growing with a vigorous trunk, attaining the classic vase-like shape of the American elm and reaching a maturity around 100 feet tall. It looks exactly like the wild American elm with oval leaves having jagged edges, brown corky bark and golden yellow fall foliage. It is a hardy tree, tolerant of drought, heat and cold, suburban air pollution and most insect pests.
Dutch Elm Disease Resistance
The Liberty elm is not fully resistant or immune to the fungal Dutch elm disease. According to the Elm Research Institute, this elm has unique plant cell structures that inhibit penetration of the fungus. In most cases, a Liberty elm will keep on growing after exposed to the disease. The Institute further reports this tree is 99% resistant to Dutch elm disease; however, occasionally but rarely some trees may succumb.
Plant Liberty elm in a full sun location, receiving at least 6 to 10 hours or direct sunlight daily. Soils should be fertile and moist, although this elm grows successfully in a wide range of soil pH and soil types, including clay, loam and deep sand. This elm selection is rated to USDA Hardiness Zones 2 through 9.
The mass devastation of native groves and street plantings of American elms in the middle of the 20th century caused many gardeners to yearn for a disease-resistant replacement. The Liberty elm is loved as a shade tree with a beautiful shape, with its high arching branches creating a "cathedral-like" canopy when viewed underneath. Clustered plantings or singular specimen Liberty elms grace avenues, parks, large residential yards and college campuses.