Ohio Trees

Bulletin 700-00

Ulmus – Elm

Elms are deciduous trees with scaly (imbricate) buds. Leaves are arranged in an alternate fashion. Leaf margins are doubly toothed and often meet in an oblique pattern at the base of the leaf. Flowers are perfect and have both functional male and female parts. The fruit is a samara (winged nutlet).

Key to Ulmus Species

Description of Species

Winged Elm–Ulmus alata

The winged elm gets its common name from the thin, corky ridges, or wings, usually found on the smaller branches. Generally, winged elms are scattered over the southern Ohio counties. The tree grows rapidly, but rarely exceeds 2 feet in trunk diameter and 50 feet in height. It forms a rather open, round-topped head. This native American elm is sensitive to Dutch elm disease and elm yellows but is somewhat resistant to elm-leaf beetle, as are the other native American elms.

The leaves are simple, alternate, 11/4—21/4 inches (3—53/4 cm) long, and half as wide. The foliage is smaller than those of any other elm native to Ohio. The leaf margin is coarsely and doubly serrate and minutely hairy. Foliage is thick, dark green, and smooth above and pale and softly downy below.

	American (White) Elm

Terminal buds are absent. Imbricate buds are reddish-brown, glabrous, and smaller than those of American elm. The bark is light brown tinged with red, and divided into irregular, flat ridges and fissures. Branches usually have two corky wings opposite each other on the stem.

The flowers appear in early spring long before the leaves unfold. The fruit ripens in the spring about the time the leaves appear. The fruit is winged; tipped with two small, incurved awns or beaks; oblong; and reddish-brown in color. Samaras are 1/3 inch (8 mm) long with long, slender stalks at the base covered with white hairs.

The wood of the winged elm is very similar to other elms: heavy, hard, strong, and difficult to split. Rope made of the inner bark was used for binding and wrapping purposes.

American (White) Elm–Ulmus americana

This is the famous shade tree of New England whose range extends to the Rocky Mountains and southward to Texas. It is common in this vast area except in the high mountains and wet bottom lands. It reaches an average height of 50—70 feet and a trunk diameter of 4—5 feet. Almost every fence row in Ohio contains some American elm. Because of its spreading, fan-shaped form and graceful, pendulous branches, the American elm justly holds its place as one of the United States' most beautiful trees.

The leaves are alternate, simple, 4—6 inches (10—15 cm) long, rather thick, and with an uneven leaf base. Foliage is glabrous and rough above but hairy to nearly glabrous below. Leaves are less pointed and not so decidedly roughened as slippery elm. Leaf margins are doubly toothed. The leaf veins are very pronounced and run in parallel lines from the midrib to leaf edge.

Terminal buds are absent. One-year-old twigs are glabrous near maturity, but are often pubescent (hairy) when young. One-year-old twigs are not rough, although they are often hairy. Buds and twigs are uniformly brownish in color.

The bark is dark gray; divided into irregular, flat-topped, thick ridges; and is generally firm, though on old trees it tends to come off in flakes. An incision in the bark ridge will show alternate layers of brown and white that some refer to as "Oreo bark". The bark is an excellent identification feature.

The greenish flowers are small, perfect, and borne on slender stalks, sometimes an inch (25 mm) long. Flowers appear before the leaves in very early spring. The fruit is a light green, oval-shaped samara (winged fruit) with the seed portion in the center and surrounded entirely by a wing. A deep notch in the end of the wing is distinctive of the species. The seed ripens in the spring and is widely disseminated by the wind.

The wood is heavy, hard, strong, tough, and difficult to split. It is used for paneling, rough construction, and veneer for baskets and crates. Like other American elms, the true American elm is susceptible to the Dutch Elm disease and phloem necrosis (elm yellows) but somewhat resistant to elm-leaf beetle feeding.

Slippery (Red) Elm

During the ‘20s and ‘30s, American elm was planted almost to the exclusion of other trees, due to the incredible urban-tolerance of Ulmus americana. The lack of diversity set U.S. cities up for the introduction of Dutch elm disease (DED) from Europe. The introduction of the exotic disease, an efficient insect carrier, and a monoculture of susceptible trees allowed this disease to spread rapidly. Many cities now ban American elm from city plantings. This is unfortunate, since urban stress is more of a threat to city trees than DED is a threat to American elm. We could increase the service life of city trees by planting sensitive American elms in limited numbers, especially in stressful sites. The really good news is that three DED-tolerant American elms have been introduced since 1990. ‘New Harmony,' ‘Princeton,' and ‘Valley Forge' are now finding their way into our cities and should again grace our city streets while reducing the impact of DED. American elm is still sensitive to phloem necrosis (elm yellows), but this disease is generally not severe in Ohio.

Slippery (Red) Elm–Ulmus rubra (fulva)

The slippery elm, or red elm, grows in all sections of the state, but is nowhere abundant. It is found principally on the banks of streams and on low hillsides in rich soils. It is a tree of small to moderate size, but not as vase-shaped as the American elm. It is usually less than 60 feet in height and 16 inches in trunk diameter, although trees of larger dimensions are occasionally found. This red elm is sensitive to Dutch elm disease and elm yellows but is somewhat resistant to elm-leaf beetle, as are the other American elms.

The thick leaves are simple, alternate, and have unsymmetrical leaf bases. Leaves are 4—8 inches (10—20 cm) long, rough above, and densely hairy beneath. Leaves are broadest at or below the middle, and taper forward to a single point or tip. Leaf margins are doubly toothed. Color of the foliage is dark green and the leaves are rough on both sides.

Scotch (Wych) Elm

Terminal buds are absent. One-year-old twigs are rough, grayish, and without wings. Twigs are lighter-colored than the pubescent buds which are rusty to nearly black in color. Flower buds are conspicuous in the winter. Winter buds are globose, reddish-orange in color, and hairy at the tip.

The bark on the trunk is usually 1 inch (25 mm) thick, dark grayish-brown, and broken into flat ridges by shallow fissures. The inner bark is used to some extent for medicinal purposes, as it is fragrant and when chewed, affords a slippery, mucilaginous substance. The tree gets it name from the slippery substance.

Flower buds are plump, reddish or orange in color, and hairy at the apex. The flowers appear in early spring, and the fruit ripens when the leaves are about half grown. The fruit consists of a seed surrounded by a thin, broad, greenish wing about 1/2 inch (13 mm) in diameter. The wood is close-grained, tough, strong, heavy, and hard.

Scotch (Wych) Elm–Ulmus glabra

Scotch elm is a native of Europe and planted for ornamental purposes. The standard tree has a broad crown with upright branches. One cultivar, the ‘Camperdown' elm, is commonly planted for its weeping habit and is often budded on a Siberian elm understock. European elms are sensitive to Dutch elm disease and elm yellows, as are the American elms. American elms are more resistant to the elm-leaf beetle than Scotch elm.

Terminal buds are absent. Buds are imbricate and 1/4 inch (6 mm) long. Branches are reddish-brown in color and hairy when young. Bark on the main stem and branches is prominently smooth and without scales or corky ridges.

Leaves are short-petioled, 31/4—61/2 inches (81/2—161/2 cm) long, and nearly as wide. Leaves are broadest above the middle, rough to the touch above, and pubescent beneath. Foliage is abruptly pointed and tends to develop three points instead of one. Leaves are dark green in color and tend to persist into late fall.

Lacebark Elm–Ulmus parvifolia

Lacebark Elm

Lacebark elm is a medium-sized tree that grows to 60 feet or more. The tree may have a vase-shaped habit or an upright, oval one. Many people prefer the vase-shaped habit, but the upright, oval habit is more storm resistant. The original common name was Chinese elm and was usually confused with Siberian elm. To avoid confusion, the name lacebark elm is now preferred. Lacebark elm is tolerant of Dutch elm disease, elm yellows, and elm-leaf beetle. The true Chinese elm (U. parvifolia) develops into a better tree for ornamental plantings than the Siberian elm. Elms are very urban-tolerant, and the lacebark elm is no exception.

Leaves of this elm are the smallest of the elms as the scientific name suggests. Leaves are a dark, glossy green and range from 3/4—2 inches (2—5 cm) long. Young leaves are pubescent beneath and glossy above. Foliage is somewhat leathery at maturity. Leaves have serrate, rather than doubly serrate, leaf margins. Leaf bases are uneven. Fall color ranges from yellow to purple and is unusually good when compared to other elms.

Terminal buds are absent. Lateral buds are less than 1/8 inch (3 mm) long and are the smallest of the elms. Twigs are very fine-textured as well. Bark is gray for young bark. Intermediate bark may exfoliate into green, orange, and gray plates. The exfoliating bark gives rise to the preferred common name.

Since flowers open in August and September, late-flowering easily separates this tree from the spring-flowering elms, such as Siberian elm, that are similar in many respects. As it matures, the winged samara is often reddish and showy against the dark foliage. Fruit matures in October and November. Fruiting time separates lacebark elm from Siberian elm as well. Most elms have conspicuous, rounded floral buds during the winter, but lacebark elm does not since it flowers in the fall and flower buds form in the summer.

This tree was introduced from Korea, Japan, and China. The large native area ranges from places where it is nearly frost-free to areas that are colder than parts of Ohio. This tree was used in southern California and sold as evergreen elm. Not surprisingly, these selections are not hardy in Ohio. Care must be taken to ensure that cold-hardy seed sources are used. ‘Ohio,' ‘Dynasty,' and ‘Pathfinder' are clones that have proven cold-tolerance. This tree is an excellent ornamental for Ohio gardens because of its glossy foliage, fall color, attractive bark, resistance to elm-leaf beetle, and disease-tolerance.

	English Elm

English Elm–Ulmus procera (campestris)

This is a large tree native of England and Europe. It reaches heights of 60—80 feet. Like most elms, it is urban-tolerant. English elm grows in an upright, oval configuration. This is quite different than the habit of the native American elm with its vase shape. The state champion English elm is on the Columbus campus of The Ohio State University and is 100 feet high and 70 feet across. European elms are as sensitive to Dutch elm disease and elm yellows as are the American elms, though the American elms are more resistant to the elm-leaf beetle than English elm. The English elm suckers freely.

The leaves are dark green and remain on the tree late into the fall. Growing only 2—3l/4 inches (5—81/2 cm) in length, the foliage is smaller than many other elms. Leaves are dark green and rough above but soft and hairy below.

Terminal buds are absent. One-year-old twigs are very hairy. Bark is dark and deeply ridged. The small branches are rough and usually covered with fine hairs. Bark on the main stems is dark and deeply plated, lacking the vertical orientation of the furrowed bark of many elms.

Siberian Elm–Ulmus pumila

The Siberian elm ranges from 40—60 feet in height. The form may be vase-shaped or an upright oval. The bark of the trunk is rough and ridged. The branches are fine, brittle, and easily broken by strong winds and ice. Litter is a constant battle.

Older twigs are seldom corky. Flowers appear in the spring. This tree is often incorrectly offered in the trade as Chinese elm. The leaves are narrowly rounded to oval in shape. Foliage is 1—3 inches (21/2—71/2 cm) in length and about half as broad. Leaves are smooth above and glabrous beneath. Foliage is dark green above and smooth and paler green below. Leaf margins have serrate or toothed margins. Petioles are less than 1/8 inch (3 mm) long.

Flower buds are globose and conspicuous during the winter months. Flowers appear early in the spring before leaves and are borne on short stalks. The winged fruit usually appears in early May and is deeply notched at the apex. The seed is off-center, nearly reaching the base of the notch.

Siberian Elm

The Siberian elm, although storm sensitive, is often planted due to its rapid growth. Siberian elm is tolerant to the Dutch Elm disease (DED) and phloem necrosis (elm yellows) but highly susceptible to the elm-leaf beetle. This tree is often defoliated in early July by the elm-leaf beetle. It has been the major source of resistance to DED in elm breeding programs. Recently it has been replaced in breeding programs by parents that are resistant to the elm leaf beetle as well as DED and elm yellows.

Rock (Cork) Elm–Ulmus thomasi (racemosa)

The rock elm is found in the northwestern part of the state and reported as far south as Greene and Lawrence counties. In Ohio's southern counties, it has been confused with the winged elm because of its close resemblance. Rock elm is found on limestone ridges, steep hillsides, and dry, gravelly soils. Its trunk extends as a central leader up through the tree, while that of the American elm divides into many codominant leaders to form the crown. Rock elm is a large plant growing to heights of 100 feet. All American elms, including rock elm, are sensitive to Dutch elm disease and elm yellows.

Terminal buds are absent. Buds are pubescent (hairy) and sharply pointed. The bark on old trees may be 1 inch (21/2 cm) thick and cut into broad, flat ridges by shallow grooves. The older branches often have corky ridges along their sides. The buds and young branches are often covered with a slight down of fine hairs.

The leaves are alternate and 2—4 inches (5—10 cm) long without a hairy margin. They resemble those of the American elm, but the veins are less prominent and straighter. Leaf margins are serrate, not doubly serrate as in the American elm. The leaf bases are uneven.

The flowers are borne in long clusters before the foliage emerges in the spring. The fruit is egg-shaped, about 1/2 inch (13 mm) long and covered with hairs. The fruit has one seed. It is called a samara, or key, and ripens in the spring as the foliage emerges.

The wood is heavy, hard, and tough. The wood is the best of the elms. It is very dense and strong. Rock elm wood is used wherever it is necessary to resist shocks. It is light reddish-brown in color with a thick, lighter-colored sapwood.

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