Once so widely planted in America that nearly every city and town has a street named after them, elm trees are a long-living deciduous hardwood tree that can live 300 years or more. Their wood is extremely hard and is used for making furniture and wood veneer. Native Americans made canoes from the mature trunks of elm trees.
Elms are some of the largest-growing of all deciduous hardwood trees. They grow 70 to 100 feet tall and have a vase-like growth habit. On mature varieties, their trunks can reach seven feet across. Elms have dark green oblong leaves with serrated edges that turn a bright yellow in autumn. Planted along sidewalks on either side of city streets, their tops arch together, forming a tunnel-like canopy over the street. They produce copious amounts of wafer-like seedpods in spring, which can fill the gutters of the street along which they are planted. Small weed saplings grow in proximity to elms due to the large number of seeds they produce each spring.
Plant elm trees in full sun or partial shade. They will tolerate a wide range of soil types, from loan to clay to sand and will tolerate either acidic or alkaline soil. They will tolerate extended flooding of their roots and are also very drought-tolerant. Elm trees are widely planted as shade trees along urban streets and in public parks, although their shallow roots can lift sidewalks, especially mature specimens.
Four main varieties of the elm tree are known to exist: the American elm (Ulmus americana), the Chinese elm (Ulmus parvifolia) and the Siberian elm (Ulmus pumila) and the Japanese elm (Ulmus japonica). Each variety has several cultivars and hybrids.
Care and Culture
Once established, elms need little cultivation, except inspection for signs of pests and diseases and the treatment thereof. They need pruning to remove lower limbs, especially on specimens planted along city streets. Pruning is also necessary to shape their canopies by removing branches growing out from the main trunk at smaller angles. They will benefit from a yearly application of fertilizer spikes and supplemental watering in times of extreme drought.
Pests and Diseases
Unfortunately, elm trees are subject to many pests and diseases. The most well-known is Dutch elm disease, which all but wiped out the native American elm population during the 20th Century. Varieties tolerant or resistant to this disease have since been developed, but they still need an integrated, active management program in order to keep the disease in check. Elms are also susceptible to leaf spot diseases, cankers and Ganoderma butt rot. Pests that infest elms include the elm borer, gypsy moth and scale.