Tree profile
Elms (Ulmus): how to identify an elm tree
A leaf whose two halves meet the stalk at different points, a doubly toothed edge and round papery seeds in spring. Then the bark tells you which elm.
In short
Elm tree identification starts with the leaf base: on American, slippery and Chinese elm the two halves of the blade meet the stalk at different points, so the base looks lopsided. Then check the edge, doubly toothed on American and slippery elm, and the fruit, a round, flat, papery seed about 1/2 inch across. In American elm, a cut through the outer bark shows alternating buff and reddish-brown layers.
- Lopsided leaf base plus double teeth: American or slippery elm. Small, singly toothed leaves with an almost even base: Siberian elm.
- Chinese (lacebark) elm flowers and fruits in late summer and fall and has mottled, jigsaw-puzzle bark.
- Hackberry also has a lopsided leaf base, but three main veins start from it and its bark carries corky warts.
Field marks at a glance
- Scientific name
- Ulmus
- Family
- Ulmaceae (elm family)
- Type
- Broadleaf, deciduous
- Leaves
- Alternate and simple. American elm: 3 to 5 inches, doubly toothed, base conspicuously lopsided. Slippery elm: 4 to 6 inches and very rough above. Siberian elm: 1 to 2 1/2 inches, singly toothed, base nearly even.
- Leaf base
- Lopsided (inequilateral) on American, slippery, rock, winged and Chinese elm, per Virginia Tech Dendrology. Siberian elm is the exception.
- Fruit
- A flat, papery, wafer-like samara, the seed in the middle of a round wing. American elm: 3/8 to 1/2 inch, deeply notched, hairy only on the edge. Slippery elm: 3/4 to 1 inch. Most elms ripen it in spring; Chinese elm in fall.
- Bark
- American elm: dark ashy gray, flat-topped ridges with diamond-shaped fissures; a cut through the outer bark shows alternating buff and reddish-brown layers. Chinese elm: mottled green, gray and orange puzzle pieces.
- Twigs and buds
- Slender, slightly zigzag. American elm buds are over 1/4 inch, reddish brown with darker-edged scales and often set a little to one side of the leaf scar.
- Form
- Open-grown American elm divides low into several ascending, arching limbs that end in drooping branchlets: the classic vase shape.
- Size and age
- American elm reaches 98 to 125 feet on good forest sites and often lives 175 to 200 years, some over 300 (USDA Forest Service).
- Native range
- American elm: Cape Breton Island, Nova Scotia west to southeastern Saskatchewan, south to central Texas and central Florida. Siberian and Chinese elm are Asian species planted in the US.
Elms (Ulmus) were the shade trees of many American city streets before Dutch elm disease, according to the USDA Forest Service. American elm is still common in woods and along rivers, and three other elms, slippery, Siberian and Chinese, turn up in yards and vacant lots. Check the leaf base first, then the teeth, then the seed, then the bark.
The four checks that name an elm
1. The leaf base. Lay a leaf flat and look where the blade meets the stalk. On American elm, Virginia Tech Dendrology describes the base as "conspicuously inequilateral": one half of the blade starts lower on the stalk than the other. Slippery, rock, winged and Chinese elm share the trait. Siberian elm is the odd one out, with a nearly even base.
2. The teeth. Run a fingernail along the edge. American and slippery elm leaves are doubly toothed: each large tooth carries smaller teeth on its edge. Siberian elm's teeth are single, and the Siberian elm fact sheet gives its leaves as only 1 to 2 1/2 inches long.
3. The seed. Elm fruit is a samara: a flat, round, papery wafer with the seed in the middle. American elm's are 3/8 to 1/2 inch across, deeply notched at the tip and hairy only on the edge. Slippery elm's are larger, 3/4 to 1 inch. Most elms flower before the leaves open and drop their seeds in spring, so a carpet of pale wafers in spring is a strong clue. The USDA Forest Service reports that American elm seed fall is usually over by mid-March in the South and mid-June in the North.
4. The bark. On the American elm fact sheet the bark is dark ashy gray, with flat-topped ridges separated by diamond-shaped fissures. The field test is a cross-section: pare a thin slice of the outer bark with a knife and look at the cut edge. American elm shows distinct, alternating buff and reddish-brown layers. Slippery elm shows no buff patches, and rock elm has no conspicuous layers.
If the leaves are out of reach, a photo of the bark or of fallen seeds is enough to get a name from Tree Identifier. The app shows no confidence score and no list of look-alikes, so check the leaf base and the teeth before you trust the answer. American elm and Japanese zelkova are both in the app's 138-species Collection.
American, slippery, Siberian and Chinese elm
| Elm | Leaf | Bark | Seeds |
|---|---|---|---|
| American (U. americana) | 3–5 in, doubly toothed, lopsided base, smooth or slightly rough above | Ashy gray, diamond fissures; buff and red-brown layers in cross-section | 3/8–1/2 in, deeply notched, spring |
| Slippery (U. rubra) | 4–6 in, doubly toothed, lopsided base, very rough above | Dark reddish brown, no buff layers | 3/4–1 in, hairy over the seed, late spring |
| Siberian (U. pumila) | 1–2 1/2 in, singly toothed, nearly even base | Light grayish brown, irregularly furrowed, often streaked | about 1/2 in, notched, spring |
| Chinese or lacebark (U. parvifolia) | up to 2 1/2 in, toothed, lopsided base, shiny | Mottled green, gray and orange puzzle pieces | about 1/2 in, notched, fall |
Rows come from Virginia Tech's American, slippery, Siberian and Chinese elm fact sheets.
A few extra marks help. Slippery elm buds are dark chestnut brown to nearly black and often rusty-hairy, where American elm buds are reddish brown with darker scale edges. Siberian elm is, in Virginia Tech's words, "typically a very bad looking tree", with broken limbs and sprouts along the trunk, and its bark is often streaked by bacterial wetwood. Chinese elm flowers in late summer and early fall, so it is the only common elm carrying fresh seeds in autumn; its trunk may become fluted.
Elm vs hackberry, ash and zelkova
Hackberry. The hackberry fact sheet also gives an inequilateral base, which is why hackberry fools people. Look for three distinct veins starting from the base of the leaf and a long, tapered tip. The bark settles it: smooth when young, then covered in corky warts that grow into rough, irregular ridges. The fruit is a small round drupe, 1/4 to 3/8 inch, turning orange-red to dark purple.
Ash. Ash bark also forms interlacing ridges in a diamond pattern, which makes the trunk of an old ash look like an elm. Look up: white ash leaves are opposite and compound, 8 to 12 inches long with about seven leaflets, and the seeds are single-winged paddles. Elm leaves are single and alternate. The ash identification page covers the species.
Japanese zelkova. Planted as a street tree, zelkova is an elm relative with a vase-shaped crown. Its fact sheet gives 1 1/2 to 2 1/2 inch leaves with single, rounded-over teeth, bark that stays smooth with many lenticels for years before flaking in small reddish-brown patches, and a tiny triangular drupe instead of a papery wafer.
Elms in winter
Without leaves, start with the twig: slender, slightly zigzag, with buds set alternately along it. American elm buds are ovate, over 1/4 inch, reddish brown with darker-edged scales, and often sit a little to one side of the twig. Then use the bark cross-section and the shape. Open-grown American elms divide low into several large, ascending, arching limbs that end in a maze of drooping branchlets, the vase shape that made them the favorite street tree. Flower buds swell from February in the South to May in Canada, and the flowers appear 2 to 3 weeks before the leaves, according to the USDA Forest Service. The winter tree identification guide has the full bud and twig key.
Dutch elm disease and what you will see
The USDA Forest Service's Silvics of North America explains why big American elms are now rare: Dutch elm disease reached the United States in 1930 in a shipment of elm logs from Europe and spread from coast to coast. A wilt fungus is carried into twigs by elm bark beetles, the smaller European elm bark beetle and the native elm bark beetle, as they feed. The disease shows as gradual wilting and yellowing of the leaves, usually followed by death of branches and then the whole tree.
That is why many surviving American elms are young or mid-sized, and why planted elms are often Asian species or disease-resistant cultivars. The Forest Service notes that American elm has twice the chromosome number of other elms, which makes it hard to cross; thousands of attempts to cross it with Siberian elm have failed. If an elm in your yard has wilting, yellowing branches in summer, ask an ISA Certified Arborist or your county extension office. For the general method that works on any tree, see how to identify trees.
Look-alikes and how to tell them apart
Hackberry (Celtis occidentalis)
Hackberry leaves are also lopsided at the base, but three distinct veins start from it, and the tip is long and tapered. The bark carries corky warts and ridges, and the fruit is a small round drupe, not a papery wafer.
Japanese zelkova (Zelkova serrata)
Zelkova's 1 1/2 to 2 1/2 inch leaves have single, rounded-over teeth and no lopsided base. Its bark stays smooth with many lenticels for years, then flakes in small reddish-brown patches; the fruit is a tiny drupe.
White ash (Fraxinus americana)
Ash bark also forms diamond-patterned ridges, but ash leaves and buds are opposite, in pairs, and each leaf is compound, 8 to 12 inches with about 7 leaflets. Elm leaves are single and alternate.
Slippery elm (Ulmus rubra)
Slippery elm leaves are larger (4 to 6 inches) and sandpaper-rough above, its buds are dark chestnut brown to nearly black and often rusty-hairy, and a cut through its outer bark shows no buff layers.
What a photo can't settle
- Elm leaves vary with sun and age, and slippery, American and rock elm overlap in size and roughness. A single leaf photo may not separate them; the buds, the seeds and the bark cross-section do better.
- Many planted elms are disease-resistant cultivars, often bred from Asian or European elms (USDA Forest Service), and they may not match any one species fact sheet.
- Dutch elm disease is a reason to call a certified arborist or your extension service, not something a photo of a leaf can diagnose.
Questions people ask
How do you identify an elm tree?
Look at where the leaf meets its stalk: on most elms one side of the blade starts lower than the other. Then run a finger along the edge for double teeth, big teeth carrying smaller ones. In spring, look for round, flat, papery seeds about 1/2 inch across under the tree.
How do you identify an elm tree by its bark?
American elm bark is dark ashy gray with flat-topped ridges and diamond-shaped fissures. Cut a small piece of the outer bark crosswise: Virginia Tech notes distinct alternating buff and reddish-brown layers. Slippery and rock elm bark lacks those layers. Chinese elm bark flakes into mottled green, gray and orange puzzle pieces.
How do you identify an elm tree without leaves?
Check the twigs: slender, slightly zigzag, with reddish-brown buds set alternately, often a little off-center over the leaf scar. Then the bark cross-section test for American elm, and the form: a vase of arching limbs ending in drooping branchlets. In early spring elms flower before the leaves open.
What is the difference between Chinese elm and Siberian elm?
Chinese (lacebark) elm has mottled, jigsaw-like bark and flowers in late summer and fall, with seeds in fall. Siberian elm has furrowed gray-brown bark, often streaked by wetwood, flowers in early spring and has a nearly even leaf base with single teeth. Both are Asian species.
Is a hackberry an elm?
No. Hackberry is a different genus, Celtis, though it shares the elm's lopsided leaf base and Virginia Tech files it in the same family. Tell them apart by the three veins that start at the base of a hackberry leaf, its warty, corky bark and its small round fruit instead of a papery wafer.
Sources
- American elm fact sheet — Virginia Tech Dendrology
- Slippery elm fact sheet — Virginia Tech Dendrology
- Siberian elm fact sheet — Virginia Tech Dendrology
- Chinese elm fact sheet — Virginia Tech Dendrology
- American Elm (Ulmus americana), Silvics of North America — USDA Forest Service
- Hackberry fact sheet — Virginia Tech Dendrology
- Japanese zelkova fact sheet — Virginia Tech Dendrology
- White ash fact sheet — Virginia Tech Dendrology