Ash Tree Identification: Leaves, Bark, Seeds, Look-Alikes

An ash tree has branches and buds in opposite pairs, compound leaves made of several leaflets, and single-winged seeds; on older trees the bark forms diamond-shaped ridges. Colorado State Forest Service lists exactly these features. Check them in this order, because each one rules out a different group of look-alikes:

• Opposite branching. Colorado State: branches and buds grow in pairs directly opposite each other, not alternating along the stem. Few trees do this, so this single check removes most candidates.
• Compound leaves. Several leaflets on a common stalk, typically 5 to 9, with smooth or finely toothed edges (Colorado State).
• Bark. Mature bark shows diamond-shaped ridges (Colorado State).
• Seeds. Female trees carry paddle-shaped seeds (Colorado State); Oregon State describes them as dry, single-winged samaras shaped like canoes.

Opposite plus compound is the combination to remember. Oregon State Extension uses the same pair: all ashes have leaves that are both opposite and pinnately compound.

• White ash (Fraxinus americana). 5 to 9 leaflets; purple fall colour (Morton Arboretum, Oregon State).
• Green ash (Fraxinus pennsylvanica). 5 to 9 leaflets; yellow or yellow-green in fall (Morton Arboretum).
• Oregon ash (Fraxinus latifolia). 5 to 7 oval leaflets (Oregon State).
• European ash (Fraxinus excelsior). 7 to 11 leaflets and black winter buds (Oregon State).
• Single-leaf ash. The exception: one simple leaf with slightly toothed edges (Colorado State).

Leaflet count varies on one tree, so count several leaves. A leaf is the whole unit from the bud to the tip, not a single leaflet; if you are unsure where a leaf starts, look for the bud at the base of the stalk.

Colorado State describes mature ash bark as having diamond-shaped ridges. Morton Arboretum describes both white and green ash bark as light grey and loosely ridged and furrowed. The Lady Bird Johnson Wildflower Center describes Arizona ash bark as deeply furrowed into ridges. Young trees have smoother bark, so on a sapling rely on the leaves and branching.

Seeds are the best confirmation when they are present. Ash seeds are single-winged samaras hanging in clusters. Oregon State gives Oregon ash samaras as about 1 inch long and green ash samaras as 1 to 2 inches. Only female trees carry them (Colorado State), so a tree without seeds can still be an ash.

A tall, broad tree with a rounded crown, grey ridged bark and feather-like leaves. Size depends on the species:

• White ash. 50 to 80 feet tall and as wide, rounded, with purplish fall colour (Morton Arboretum).
• Green ash. 50 to 60 feet tall and 25 to 40 feet wide, yellow in fall, common in moist lowland sites and as a street tree (Morton Arboretum, Oregon State).
• European ash. 85 to 100 feet (Oregon State).
• Raywood ash. 30 to 40 feet with red fall colour; Oregon State calls it the most commonly planted ash cultivar.
• Oregon ash. A narrow, dense crown, in seasonal wetlands and along streams (Oregon State).
• Arizona ash. Usually no taller than 40 feet in cultivation and about 50 feet at most (Wildflower Center).

Two groups, and one check separates each from ash.

Compound leaves, but alternate. Oregon State lists black and English walnut, black locust, honeylocust, European mountain-ash (rowan), sumac and golden raintree. Their leaves look like ash leaves, but they alternate along the twig instead of growing in pairs. Mountain-ash is the one people get wrong most, because of its name: Morton Arboretum describes European mountain-ash as having alternate leaves with 9 to 15 leaflets and clusters of small red berry-like fruit, and places it in the rose family, not with the true ashes.

Opposite, compound, but not ash. Oregon State names boxelder and elderberry. Boxelder is a maple: Morton Arboretum gives it 3 to 5 (sometimes 7) irregularly toothed leaflets, young stems that are green with a white waxy coating, and seeds in pairs of wings. Ash has 5 to 9 leaflets, grey twigs and seeds with a single wing.

Look at one leaf. Morton Arboretum describes American elm leaves as single, alternate, oval and pointed, with doubly toothed edges and a base that is shorter on one side of the midrib than the other. An ash leaf is compound, made of several leaflets, and grows in opposite pairs.

The whole tree helps too. Morton describes American elm as vase-shaped, with branches spreading like a fountain, and its seeds as small oval samaras; ash has a rounded crown and single, paddle-shaped wings.

Use the same checks: opposite branching, compound leaves and single-winged seeds. The native species there is Arizona or velvet ash (Fraxinus velutina). The Lady Bird Johnson Wildflower Center lists its range as Arizona, California, New Mexico, Nevada, Texas and Utah south to Jalisco in Mexico, growing on desert and chaparral streambanks and in canyons.

Features to look for: leaflets often covered with velvety hairs underneath, though some trees are hairless; leaflets that vary a lot in shape; bark deeply furrowed into ridges; yellow fall colour; and a tree usually no taller than 40 feet in cultivation (Wildflower Center). The Center notes the species is extremely variable across its range, so rely on branching and seeds rather than leaf shape alone.

• Vermont and the Northeast. Green, black and white ash (Vermont Invasives).
• Oregon, Washington and northern California. Oregon ash is the only native ash; white, green and European ash and the Raywood cultivar are planted (Oregon State).
• Colorado. Colorado State's identification page covers the general features above and notes the single-leaf ash exception.
• Desert Southwest. Arizona ash (Wildflower Center).

Knowing whether a tree is an ash tells you whether it is at risk from emerald ash borer, an invasive beetle. Oregon State Extension says all ash trees are susceptible, that the pest was first sighted in Oregon in June 2022, and that it has caused extensive death of native ash species. Morton Arboretum calls white ash very susceptible and no longer recommends planting it in the Chicago region; affected trees usually need removal or regular insecticide treatment.

Colorado State Forest Service and Vermont Invasives both publish their ash identification pages as part of their emerald ash borer programmes. If you confirm an ash and see decline, contact your state forestry agency or extension office; they can confirm the pest and explain treatment options.

The branching pattern is what a single leaf photo misses. For the best result, photograph a twig tip showing two leaves attached opposite each other, then one whole leaf with all its leaflets, then the bark at chest height, and any seed clusters. With those photos PlantLens can separate ash from boxelder, walnut or mountain-ash, and you can check its answer against the four features above.

For other trees, see identifying trees by leaf and identify a tree by bark.

Research and drafting for this page were done with the help of AI, and every figure was then checked line by line against the sources listed at the end of the page. Sources were opened on 2026-09-25. If you find a mistake, tell us and we will correct it.