Elm tree: how to identify one, the main types, and what Dutch elm disease looks like

At a glance

What an elm tree looks like

Check these four features together. Any one of them can mislead on its own; all four together are diagnostic.

• Uneven leaf base. One side of the leaf blade meets the stalk noticeably lower than the other. The Morton Arboretum describes the elm leaf as shorter on one side of the center vein than the other.
• Doubly serrated margin. Native elms have large teeth that each carry smaller teeth. The Morton Arboretum describes tooth-within-tooth margins, though Siberian elm leaves are singly toothed (Wisconsin DNR) and lacebark leaves simply serrate (NC State Extension).
• Two-ranked, alternate leaves with straight, parallel side veins running out to the teeth. Leaves are oval to elliptical with a pointed tip and often feel rough on top.
• Samaras. Elm seeds are flat, round or oval papery wafers with the seed in the middle. American elm samaras mature in spring as the leaves reach full size (NC State Extension); lacebark elm flowers in late summer or fall.

From a distance, a mature American elm is unmistakable: the trunk divides low into several limbs that rise and arch outward into a vase or fountain shape. That form made it a favorite street tree.

Identifying elms in winter

Without leaves, look at twigs, buds and bark. Slippery elm twigs are downy, while American elm stems are smooth and brown (NC State Extension). Siberian elm twigs are nearly hairless, with black hairs on the bud scales, and its flowers open in spring before the leaves (Wisconsin DNR). Old samaras caught in the bark or on the ground nearby confirm the genus.

For a quick leaf check, run a specimen through the tree and shrub leaf ID key; for winter trees, compare bark using how to identify a tree from bark alone.

Types of elm trees

American elm (Ulmus americana)

Native to eastern North America, from Newfoundland to Manitoba and south to Florida and Texas, and hardy in zones 3–9 (NC State Extension). Leaves are 4–6 inches, rough-textured, with an asymmetrical base. The bark is dark gray and divided into flat, braided ridges. The vase-shaped crown, 60–80 feet tall in the open, is the fastest identification on a large tree.

Slippery elm (Ulmus rubra)

Larger leaves (4–8 inches) that feel rough on top because of minute hairs, and downy twigs. NC State Extension describes slimy red inner bark, which gives the tree its common name, under gray bark of narrow flat ridges and shallow furrows. This is the tree people mean when they search for how to identify slippery elm.

Siberian elm (Ulmus pumila)

Small (0.8–2.6 inch), singly toothed leaves with a tapered or rounded base. Per the Wisconsin DNR, its seeds develop and germinate quickly, forming dense thickets along roadsides, pastures, grasslands, stream banks and prairies, and the state classifies it as a Restricted invasive species. The DNR flags lacebark (Chinese) elm as its main look-alike.

Lacebark or Chinese elm (Ulmus parvifolia)

The ornamental elm. NC State Extension lists it for zones 5b–10a and notes it resists Dutch elm disease, Japanese beetles and elm leaf beetles, though it can self-seed and its wood breaks in wind and ice. The mottled, exfoliating bark and late-summer-to-fall flowering separate it from Siberian elm, which flowers in spring before the leaves and has furrowed bark.

Elm look-alikes

Dutch elm disease: how to recognize it

Dutch elm disease (DED) is a vascular wilt caused by the fungi Ophiostoma ulmi and the more aggressive O. novo-ulmi. The Morton Arboretum notes it was introduced to the U.S. in the early 1930s and has killed hundreds of thousands of elms. University of Minnesota Extension describes two ways it spreads: elm bark beetles (the native Hylurgopinus rufipes, the smaller European Scolytus multistriatus and the banded elm bark beetle) carry spores from infected wood to healthy twigs, and the fungus moves through root grafts between neighboring elms.

Symptoms, in the order they appear

1. Flagging: leaves on one branch or one section of the crown wilt, curl, yellow and then brown, usually in late spring or summer, while the rest of the tree looks normal.
2. Spread: more branches flag over weeks; in a root-graft infection, the whole tree can wilt quickly.
3. Brown streaking: peel the bark from a wilting branch and you will see brown streaks along the outer sapwood, the key field sign described by UMN and Penn State Extension.

The Morton Arboretum notes DED is difficult to diagnose in the field, so send a sample of a wilting live branch to a plant diagnostic lab for a firm answer. Elm yellows, a separate phytoplasma disease, yellows the whole crown more uniformly and turns the inner bark a butterscotch color that can smell of wintergreen (Penn State Extension).

What a dead elm looks like

An elm killed by DED has a wilted, brown or bare crown; leaves yellow, brown and drop early, and UMN notes fallen leaves strewn over the lawn in spring or summer. Very susceptible trees can die the year they are infected (Morton Arboretum). Dead and dying elms with bark attached are breeding sites for elm bark beetles, so prompt removal and disposal of the wood protects nearby elms.

Managing Dutch elm disease

Per University of Minnesota Extension, management depends on how early the disease is caught:

• Early, single-branch infection: an arborist can prune out the infected limb at least 5 feet, preferably 10 feet, below the last sign of streaking. The Morton Arboretum notes pruning works best when no more than 5% of the tree shows symptoms.
• Advanced infection: remove the tree and debark, chip, bury or burn the wood per local rules so beetles cannot breed in it.
• Prevention for high-value trees: trained arborists can inject systemic fungicides, which work best before infection or at its very earliest stage. Depending on the product, treatment is repeated every 1 to 3 years.
• Root grafts: where elms stand close together, an arborist can sever root grafts between a diseased and healthy tree before removal.

Because elm bark beetles breed in dead and dying elm wood with the bark attached, don't keep or move elm firewood with bark on (Morton Arboretum). See when to prune deciduous trees for timing by species, and tree cankers if you are seeing sunken bark rather than wilting.

Disease-resistant elms worth planting

Elms are back on planting lists because of decades of breeding. The Morton Arboretum's elm cultivar guide covers its own Dutch-elm-disease-resistant hybrids (Accolade, Triumph, Commendation, Vanguard and Danada Charm) and resistant cultivars of the native American elm such as 'Valley Forge', 'New Harmony', 'Princeton' and 'Jefferson'. All four American elm cultivars also appear on Penn State Extension's list of DED-resistant cultivars.

Two cautions: resistant is not immune (UMN Extension, Morton Arboretum), and planting many elms of one clone repeats the monoculture mistake that let DED sweep through cities. Mix elms with other species. For other large trees, see oak tree care and the trade-offs in fast-growing shade trees.

Planting and caring for an elm

• Zones: American elm 3–9; slippery elm 3–9; lacebark elm 5–10.
• Site: full sun and room to spread. NC State Extension notes American elm adapts to both wet and dry sites and tolerates compaction and urban conditions.
• Planting: plant in spring or fall with the root flare at grade, and water regularly while it establishes. Method: how to plant a tree the right way.
• Pruning: train young elms to a strong central structure and remove narrow, tight forks early.
• Watch list: Dutch elm disease, elm yellows, and elm leaf beetle feeding. Healthy, watered trees cope best.

Common mistakes

Frequently asked

How do you identify an elm tree?

Look at a leaf first: elm leaves are alternate and oval with a pointed tip, a lopsided base where one side meets the stalk lower than the other, and usually tooth-on-tooth (double) serrations. Confirm with flat, round papery seeds and, on mature American elms, a vase-shaped crown with gray, interlacing ridged bark.

What do elm tree leaves look like?

Elm leaves are simple, oval to elliptical, and about 1 to 8 inches long depending on species, with straight parallel side veins and a pointed tip. The base is uneven and the margin is usually doubly toothed. Many native elm leaves feel rough like sandpaper on the upper surface.

How do you identify a slippery elm tree?

Slippery elm has large leaves, about 4 to 8 inches, that are rough on top, downy twigs, and gray bark with narrow flat ridges and shallow furrows. Its inner bark is red and slimy, which is where the name comes from (NC State Extension).

What is Dutch elm disease?

Dutch elm disease is a fungal wilt caused by Ophiostoma ulmi and O. novo-ulmi that blocks an elm's water-conducting tissue. Elm bark beetles carry the spores between trees, and the fungus also spreads through grafted roots of nearby elms. Early signs are wilting, yellowing branches and brown streaks under the bark.

What does a dead elm tree look like?

An elm killed by Dutch elm disease has a wilted crown whose leaves yellowed, browned and dropped early, often in late spring or summer. Dead trunks and branches with bark attached are where elm bark beetles breed, so UMN Extension and the Morton Arboretum advise prompt removal and burying, debarking, burning or chipping the wood.

Are there elm trees resistant to Dutch elm disease?

Yes. The Morton Arboretum and Penn State Extension list resistant American elm cultivars such as 'Valley Forge', 'New Harmony', 'Princeton' and 'Jefferson', and the Morton Arboretum has released several resistant hybrid elms. Lacebark elm is also highly resistant. Resistance lowers risk but does not make a tree immune.

Is Siberian elm invasive?

In many areas, yes. Per the Wisconsin DNR, Siberian elm seeds develop and germinate quickly, forming dense thickets along roadsides, pastures, grasslands, stream banks and prairies, and Wisconsin classifies it as a Restricted invasive species. It is not a good choice for new plantings; native or resistant hybrid elms are better options.

Sources

1. Dutch elm disease, University of Minnesota Extension
2. Dutch elm disease, The Morton Arboretum
3. Elm cultivars, The Morton Arboretum
4. Elm diseases, Penn State Extension
5. Ulmus americana (American elm), NC State Extension Gardener Plant Toolbox
6. Ulmus rubra (slippery elm), NC State Extension Gardener Plant Toolbox
7. Ulmus parvifolia (Chinese elm, lacebark elm), NC State Extension Gardener Plant Toolbox
8. Siberian elm (Ulmus pumila), Wisconsin Department of Natural Resources

Read next