Elm is a beautiful, large tree that is valued for its lumber and shade. Elms are common in North America, Europe, and some parts of Asia. Some North American elms have the shape of a vase, spreading out gradually from the bottom. In other elms, the limbs branch out from the top of the trunk in the form of an umbrella. Many elms reach heights of 80 to 100 feet (24 to 30 meters). Some elms live more than 150 years.
Elms grow naturally along streams and the lower slopes of hillsides where the soil is well drained. However, they can grow in a variety of soils and terrains. In urban areas, elms are often planted along streets and in parks. They also are widely used in landscaping.
Elm wood is tough and hard, and usually light-brown in color. It does not split easily and is useful for making barrels, farm tools, fence posts, hockey sticks, furniture, and boats. It can also be used for fuel.
Kinds.
There are about 20 species of elms. The American elm, also called the white elm, is the most widespread species in North America. It grows naturally throughout southeastern Canada and the eastern half of the United States. The small, greenish flowers of the American elm appear in the spring, before the leaves grow. The fruits, each with a little wing around it, fall to the ground as the leaves open. Most other elms also produce their flowers in the spring. Some species, including the September elm and the cedar elm, produce flowers and seeds in the fall.
Other important elms found in North America include the rock elm, the slippery elm, and the English elm. The rock elm gets its name from its extremely hard and tough wood. It is also called the cork elm because its bark is corky. The rock elm grows chiefly in the Great Lakes region. The slippery elm has a natural range almost as extensive as the American elm. Slippery elms have rough, hairy leaves and a gluey inner bark. The tall English elm is native to England and western Europe. The English elm has been widely planted in North America since colonial times.
Diseases.
Dutch elm disease and phloem necrosis kill many elms each year. Dutch elm disease, so named because it was first observed in the Netherlands in 1919, was first noted in North America in 1930. Since then, it has spread through most of the range of the American elm, thus causing concern for the tree’s future. The disease is caused by a fungus and spread primarily by native elm bark beetles and European elm bark beetles. It can also be transmitted from the roots of an infected tree to the roots of a nearby elm. Prompt removal of infected branches and trees is the most commonly used procedure for slowing the spread of the disease. See Dutch elm disease.
Species of elms that are resistant to Dutch elm disease have been planted in the United States as a substitute for the American elm. They include the Siberian elm and the Chinese elm. Several other potentially resistant elms have been identified, most of them hybrids of European and Asian species.
Phloem necrosis is caused by a microbe carried by insects called leafhoppers. An infected tree cannot be recognized until its leaves begin to turn yellow and fall. By then it is too late for effective treatment.
