Ulmus americana aka American Elm

American elm, Ulmus americana, is a large deciduous tree in the elm family, Ulmaceae. It grows wild across eastern and central North America. Its range runs from Newfoundland and Manitoba south to Florida and Texas. Kew extends it into northern Mexico. In the wild it often grows in wetlands. Other common names include white elm, water elm, gray elm and soft elm.

In gardens the tree usually reaches 60 to 80 feet (18 to 24 m) tall. Some sources give heights up to 90 feet (27 m). Spread runs from 30 to 70 feet (9 to 21 m), depending on the tree's shape. The classic form is a vase with arching branches. Some trees grow broad and rounded like an oak, while others stay narrow. Forest trees develop a tall, clear trunk, while open-grown trees often fork low. Old trunks can reach 7 feet (2 m) across and may form buttresses at the base. Young trees grow fast.

The dark gray bark has flat, braided or criss-crossing ridges. On old trees it flakes off in small plates. Twigs are slender, reddish brown and slightly zigzag. The leaves are simple, alternate and 3 to 6 inches long. They feel rough, have doubly toothed edges, and have a lopsided base. They turn a soft yellow or yellowish brown in fall. Small greenish-red flowers hang in clusters in late winter or early spring, before the leaves open. Flat, papery samaras with hairy edges follow soon after. Trees bear seed only after about 15 years of age.

American elm does best in full sun and rich, moist, well-drained soil. It also accepts light shade. It copes with wet and dry sites, clay or sand, and acid or alkaline soils. Once established it tolerates drought, soil compaction, ozone and urban stress. It is hardy in USDA zones 2 to 9. Its fibrous roots make young trees easy to transplant. However, the roots are shallow and can lift into large surface roots.

This tree once lined city streets and lawns across North America, and some trees lived over 300 years. Birds and mammals eat the seeds, and the tree offers nesting sites. It hosts the caterpillars of mourning cloak, painted lady, eastern comma and question mark butterflies. The hard, heavy wood has served for lumber, furniture, barrel hoops and firewood. People have used the fibrous inner bark for string and rope.

Dutch elm disease has killed most large American elms. Bark beetles carry this fungus, and no cure exists. Gardeners should plant resistant cultivars and watch for symptoms. Phloem necrosis, also called elm yellows, is another fatal disease. Wetwood, cankers, leaf spots, powdery mildew and verticillium wilt also occur. Pests include elm leaf beetles, leafminers, bark beetles, borers, aphids and scales. The wood breaks easily, so young trees need pruning for a strong structure. The seeds and leaves also create litter. Plants For A Future lists no known hazards. It records the leaves as edible raw or cooked. The red inner bark has been brewed as a coffee substitute.