American Elm

About American Elm (Ulmus americana)

American elm is a large deciduous tree native to eastern North America that used to be one of the most common, beloved shade trees in cities and towns across the United States. It thrives in rich soil and can tolerate both wet and dry conditions, allowing it to grow in forests, floodplains, parks, and urban landscapes.

American elm supports a variety of wildlife. The seeds are eaten by birds and small mammals, while the foliage serves as food for numerous native insects. The extensive root system also helps stabilize soil and reduce erosion.

One of the greatest challenges facing the species has been Dutch elm disease, a fungal disease spread primarily by elm bark beetles. The disease blocks the movement of water within the tree, causing branches to wilt and eventually die. Since its introduction to North America in the 1900s, Dutch elm disease has dramatically reduced American elm populations, although disease-resistant cultivated varieties and surviving mature trees continue to preserve the species.

American elm also holds cultural and historical significance. In Haudenosaunee tradition, the elm is associated with creation stories and the origins of humankind. The species is also linked to American history through the famous “Washington Elm” in Cambridge, Massachusetts. This marked the site where George Washington first took command of the Continental Army in 1775, though this association is based on local tradition rather than definitive historical documentation.

Identification

American elm is most easily recognized by its distinctive vase-shaped growth form. Mature trees often have a broad crown with large branches that arch upward and outward before drooping gracefully.

The leaves are dark green, oval-shaped, and arranged alternately along the branch. They have sharply serrated edges and a pointed tip. One of the best identification features is the asymmetrical leaf base, where one side of the leaf attaches to the petiole lower than the other.

The bark of young trees is relatively smooth with a grayish-brown hue. As trees mature, the bark becomes darker and develops deep furrows separated by ridges that form a characteristic diamond-shaped pattern.

In early spring, small clusters of greenish-red flowers appear before the leaves emerge. Shortly afterward, round papery samaras (seed structures) develop and are often dispersed by wind before summer begins.

Phenology Highlights

Phenology is the study of recurring seasonal events in plants and animals. The following phenophases, distinct and observable stages in the annual life cycle of a plant or animal, are monitored as part of the National Parks of Boston Tree Monitoring Program.

Breaking Leaf Buds

American elm is one of the earlier trees to leaf out in spring. Leaf buds swell and open to reveal light green leaves that emerge folded before expanding.

Leaves & Early Season Leaf Expansion

Mature leaves of the American Elm. NPS Photo / W. Kaselow

American elm leaves expand rapidly in spring, forming a dense canopy. Mature leaves are dark green, oval-shaped, and have sharply serrated edges.

Colored Leaves & Falling Leaves

Daryl_mitchell via Wikimedia Commons CC BY-SA 2.0. https://creativecommons.org/licenses/by-sa/2.0/

In autumn, American elm foliage typically turns yellow before dropping.

Flowers or Flower Buds & Open Flowers with Pollen Release

Flowers of an American elm. NPS Photo / W. Kaselow

American elm produces flowers very early in spring, often before leaves emerge. Small clusters of greenish to reddish flowers appear along the branch. These flowers provide an important early-season food source for pollinators.

American elm is primarily wind pollinated. Pollen release occurs shortly after flowers open, often before the tree has fully leafed out. The lack of leaves helps pollen travel more effectively through the air.

Fruits

Fruits of the American Elm. NPS Photo / W. Kaselow

Following pollination, flattened circular fruits called samaras develop quickly. Each samara contains a single seed surrounded by a thin papery wing. The samaras have long hairs along their margins and are hairless elsewhere.

Ripe Fruits & Recent Fruit or Seed Drop

As they ripen, samaras change from green to tan and become dry and papery.

American elm seeds are dispersed by wind. Once ripe, the lightweight samaras often fall or are carried away. Look for papery winged seeds beneath the canopy.

Learn More

• Ulmus americana (American elm): Go Botany. (n.d.). Gobotany.Nativeplanttrust.Org. Retrieved September 4, 2026.
• Ulmus americana - Plant Finder. (n.d.). Missouri Botanical Garden. Retrieved September 4, 2026.
• Ulmus americana (American Elm, Gray Elm, Soft Elm, Water Elm, White Elm) | North Carolina Extension Gardener Plant Toolbox. (n.d.). North Carolina Extension Gardener Plant Toolbox, North Carolina State. Retrieved September 4, 2026.
• Nolan, J., & Expert, G. (2022, February 18). American Elm Tree: Leaves, Bark (Pictures) - Identification and Care. Leafy Place.
• “The Washington Elm fell near 100 years ago, living symbol of liberty and site of reverence.” (2023, October 23). History Cambridge.
• “The Iroquois Creation Story.” (1995) The Norton Anthology of American Literature. Eds. Nina Baym et al. pp. 28-30. Retrieved September 4, 2026.

National Parks of Boston Tree Monitoring Program

By observing seasonal changes in trees, volunteers help scientists better understand how plants respond to changing environmental conditions over time.

Where this belongs

• Boston Harbor Islands National Recreation Area
• Boston National Historical Park

Where this page came from

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