elm

The English elm has the typical elm leaf, oval, toothed, and distinctly lopsided. The seed is surrounded by a yellowish petal-like wing.

Any of a group of trees found in temperate regions of the northern hemisphere and in mountainous parts of the tropics. All have doubly-toothed leaf margins and clusters of small flowers. (Genus Ulmus, family Ulmaceae.)

Species include the wych elm (Ulmus glabra), native to Britain; the North American white elm (U. americana); and the red or slippery elm (U. fulva). Most elms (apart from the wych elm) reproduce not by seed but by suckering (new shoots arising from the root system). This nonsexual reproduction results in an enormous variety of forms.

The fungus disease Ceratocystis ulmi, known as Dutch elm disease because of a severe outbreak in the Netherlands in 1924, has reduced the numbers of elm trees in Europe and North America. It is carried from tree to tree by beetles. Elms were widespread throughout Europe to about 4000 BC, when they suddenly disappeared and were not common again until the 12th century. This may have been due to an earlier epidemic of Dutch elm disease. In 1997 the US National Arboretum developed a Valley Forge elm that is resistant to the disease. It is expected to be available to the public in 2000.

The American elm (U. americana) and slippery elm (U. rubra) are native to E North America.