American Elm Leaf Identification: Uneven Base, Double Teeth

An American elm leaf is alternate, simple, oval and pointed, with doubly toothed edges and a lopsided base (Morton Arboretum). Wikipedia gives the length as 7 to 20 cm, about 3 to 8 in.

Check three things:

• The base. One side of the blade starts lower on the stalk than the other; the Morton Arboretum puts it as the leaf being shorter on one side of the center vein. This lopsided base is the quickest elm signal.
• The teeth. Each large tooth carries smaller teeth on it (double serration). The National Park Service describes the margin as deeply serrated.
• The arrangement. Leaves alternate along the twig; the National Park Service notes this shows clearly in winter and early spring on the reddish-brown twigs.

In fall the leaves turn yellow (Morton Arboretum) or greenish yellow (National Park Service).

Both have large, double-toothed, lopsided leaves, so use touch and color:

• Leaf surface. Wikipedia describes slippery elm leaves as rough above but velvety below.
• Buds. Slippery elm has chestnut-brown or reddish hairy buds and downy twigs (Wikipedia).
• Inner bark. Slippery elm's inner bark is red and slimy, which gives the tree its name (Wikipedia). Do not strip bark from a living tree to test it; the bud and leaf checks are enough.
• Seed. Slippery elm's samara has red-brown hairs on the central seed and is otherwise smooth (Wikipedia).

The USDA Wood Handbook groups American and slippery elm together as soft elm and lists slippery elm's other name as red elm.

Siberian elm (Ulmus pumila) is the most likely mix-up, since Wikipedia says it has become invasive from central Mexico across the eastern and central United States to Ontario. The leaf separates them quickly (Wikipedia):

• Size. Siberian elm leaves are 2 to 8 cm long, often under half the length of an American elm leaf.
• Teeth. Usually single-toothed rather than double.
• Base. Much closer to symmetrical.
• Seed. Round samaras 1 to 2 cm long.

A small, evenly single-toothed leaf with a near-symmetrical base points to Siberian elm.

When leaves are gone, the shape does the work. WunderWoods, a sawmill that handles elm logs, calls shape the best way to identify American elm without leaves: a short trunk that separates into many branches with no clear leader, fanning out like a vase, with lower branches sometimes turning up at the ends. The Morton Arboretum describes branches like spreading fountains, and the National Park Service notes the tree splits into large branches fairly low and weeps at the edges. Mature bark is rough and furrowed (Morton Arboretum); WunderWoods describes it as shallow, stringy and flaking in spots. In early spring the reddish flowers come before the leaves, followed by the papery, round-winged seeds (National Park Service; Wikipedia).

Still widespread, but far less common than it was. Dutch elm disease has caused die-offs across the range since the 1920s (Wikipedia), and the USDA Wood Handbook says Dutch elm disease and phloem necrosis have killed hundreds of thousands of trees. Wikipedia estimates only about 1 in 100,000 American elms is tolerant of the disease, though the species holds on in many places and is the state tree of Massachusetts and North Dakota. For planting, the Morton Arboretum recommends disease-resistant cultivars with the classic vase form: Jefferson, New Harmony, Prairie Expedition, Princeton and Valley Forge.

WoodLens can identify an elm from a leaf, bark or whole-tree photo. For the lumber, see our American elm wood page.

This page was drafted with AI help, and every figure was checked line by line against the sources listed.