American elm

Ulmus americana
Family: Ulmaceae

Natural Historyamerican elm branch
Leaves and branch of American elm
Photo credit: Larry Korhnak, University of Florida

The American elm is a moderately large tree, 80-120 feet in height and 2-5 feet in diameter.  It usually has a heavily buttressed bole that divides several feet above the ground into a number of gracefully arching limbs, forming an attractive, vase-like or spreading crown of pleasing symmetry and beauty.  It is a fast-growing tree that once shaded many streets in the eastern United States.  Those avenues changed dramatically, however, when Dutch elm disease reached the U.S. in 1930 in a shipment of elm logs from Europe. The disease quickly spread across the northeastern states, killing millions of American elms in forests and cities.

Dutch elm disease is caused by a fungus that disrupts the vascular system, causing wilting and eventual death within 2 months. The fungus is spread by bark beetles and root grafts. To prevent the spread of the disease, infected trees need to be quickly removed and the root connections to neighboring trees need to be cut. Dutch elm disease has not yet been detected in Florida, but arborists watch elms closely for the symptoms so any outbreak can be quickly quarantined and controlled.

Habitat & Range

Although in decline, the American elm is found throughout eastern North America extending west to Manitoba and Texas. It is common on bottomlands, alluvial flats, margins of streams, ponds, swamps, and lakes, and on moist fertile slopes and uplands in association with other hardwoods. It thrives in loamy soils, but doesn’t have a high tolerance for prolonged flooding during the growing season.  It has intermediate shade tolerance yet prefers full sunlight and grows well with sugarberry, green ash, and sycamore, but it is shaded out by sugar maple and American beech.

Wildlife Use

American elm is a prolific and early seed producer. The flower buds, flowers, and fruit are eaten by gray squirrels. The seeds are also eaten by mice, squirrels, opossum, ruffed grouse, bobwhite, and partridge.

Human Use

The American elm is a favorite and highly prized ornamental street and shade tree in many U.S. cities.  The wood is very durable and is suited for use in the manufacture of kitchenette furniture, flooring, baskets, and woodenware. Its toughness and flexibility also make it well suited for the making of hockey sticks.


 

Identifying Characteristics

Size/Form: American elm is a large tree that reaches heights of 120 feet. The bole is buttressed with prominent root flares. The drooping branches fan out creating an umbrella-shaped crown.
Bark: A young tree has dark grayish-brown outer bark, buff inner bark, and shallow intersecting elliptical to diamond-shaped fissures. As the tree matures the bark becomes ash-gray and scaly.
Twigs: The twigs are slender, reddish-brown to dark brown, and glabrous or sparsely pubescent.
Leaves: The leaves are simple, alternately arranged, and deciduous. The leaves are 3 to 6 inches long and 2 to 3 inches wide. The leaves are obovate with a very inequilateral base looking like someone took a bite out of one side. The leaves taper to an acute apex. The leaf surface is dark green and smooth above while paler and pubescent (or rarely glabrous) below. The leaf margin is coarsely doubly serrate. The color changes to yellow in autumn. Petioles are short and stout, about ¼ inch long.
Flowers: The flowers of this tree are perfect and without petals, in clusters on long stalks. They appear in early spring and are not very noticeable.
Fruit: The samara contains a single, flattened seed surrounded by a narrow wing that is green or sometimes orange-red in color. The seeds are oval to oblong, about ½ inch long. The wings are deeply notched at the tip. Margins have dense white pubescence along the wing.
Similar Trees on the Florida 4-H Forest Ecology Contest List:
  • The leaves of American beech are similar, but the trees have very different bark.

 

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