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

Ash tree bark identification starts with the pattern on a mature trunk: the bark forms interlacing ridges that meet and part again, leaving diamond-shaped furrows between them. The Colorado State Forest Service lists "diamond-shaped ridges" as the mature-bark mark of ash, and the Minnesota DNR describes older white ash as greenish-brown with diamond-shaped fissures.

Two cautions make the bark check reliable:

• Age. Young ash bark is thin and fairly smooth. The Minnesota DNR says white ash is "nearly smooth" on young growth, so a sapling will not show diamonds yet.
• Other furrowed bark. Many trees have ridged gray bark, so treat bark as the first clue, not the last. Confirm with the branches and leaves.

All three agencies ranking for this search use the same three-step check:

• Opposite branching. Branches and buds grow in pairs directly across from each other. Virginia Tech's dendrology primer notes that only a short list of trees do this: maple, ash, dogwood, the honeysuckle family (Caprifoliaceae) and horsechestnut, remembered as "MAD Cap Horse". In winter, the paired buds and twigs are enough.
• Compound leaves. Each leaf is a stalk carrying several leaflets, typically 5 to 9 (Colorado State Forest Service); the Minnesota DNR says "five to many". Count leaflets on the whole leaf, not the single leaflets, which is the most common beginner mistake.
• Leaflet edges. Smooth or finely toothed.

If a tree passes all three, it is very likely an ash. The one exception in North America is singleleaf ash (Fraxinus anomala): some, though not all, of its leaves are simple rather than compound, and Wikipedia describes each leaflet as oval to round with toothed edges.

The Minnesota DNR separates the three northern species by leaflets, bark and seeds:

• White ash (Fraxinus americana) - leaves 8 to 12 inches with 5 to 9 stalked, sharp-pointed leaflets that are dark green above and pale, whitish beneath; the seed wing looks like a canoe-paddle blade, 1 to 2 inches long; mature bark greenish-brown with diamond fissures.
• Green ash (Fraxinus pennsylvanica) - leaves 10 to 12 inches with 7 to 9 stalked leaflets; bark dark brown or gray tinged with red and strongly furrowed; the seed wing extends past the middle of the seed.
• Black ash (Fraxinus nigra) - the longest leaves, 9 to 16 inches, with 7 to 11 leaflets that have no stalks except the end one; bark grayish with thin scales that rub off easily; favours cold, wet sites.

In the Southwest, the common native species is velvet ash, also sold as Arizona or Modesto ash (Fraxinus velutina). Wikipedia describes it from southern California east to Texas and into northern Mexico, with leaves 10 to 25 cm long of five or seven (sometimes three) leaflets, rough gray-brown fissured bark and velvety-downy shoots. Rub a new shoot: the soft down is the quick field check.

• Hickory. Shagbark hickory also has pinnate leaves, usually five leaflets, but they are alternate on the twig, the three end leaflets are much larger than the bottom pair, and the leaves run 30 to 60 cm long (Wikipedia). Mature shagbark bark peels in long strips rather than forming diamonds, and the fruit is a nut in a thick four-part husk, not a winged seed.
• Boxelder (Acer negundo). The one real opposite-leaved look-alike. Wikipedia calls its leaves "ash-like" but gives only three to seven leaflets, the young shoots are green with a whitish to pink or violet waxy bloom, and the seeds are paired maple-style samaras.
• Mountain-ash (Sorbus). Pinnate leaves and a misleading name, but Wikipedia is explicit that Sorbus is not closely related to true ash (Fraxinus). It is not on Virginia Tech's short list of opposite-leaved trees, and it carries clusters of berry-like fruits (pomes) instead of winged seeds.
• Elm. American elm leaves are simple, not compound: alternate, 7 to 20 cm long, doubly toothed and lopsided at the base (Wikipedia). The seed is a round papery wafer, not a paddle.
• Walnut and other alternate compound leaves. Any tree whose compound leaves alternate up the twig is not an ash.

Most of the pages that rank for this search were written for emerald ash borer programs. Wikipedia reports that the beetle, introduced from eastern Asia in wood packing material around the late 1980s to early 1990s, has killed tens of millions of trees in 22 US states and threatens some seven billion ash trees in North America. In Europe, ash dieback caused by the fungus Hymenoscyphus fraxineus has infected about 90% of Denmark's ash trees.

Knowing a tree is ash is the first step before any treatment or removal decision. For signs of infestation and treatment options, contact your state forest service or a certified arborist; this page covers identification only.

Ash is also a valuable timber, which is why dead and removed trees end up as firewood and boards. The USDA Wood Handbook (Table 5-3b, 12% moisture) gives side hardness of 1,320 lbf for white ash, 1,200 lbf for green ash and 850 lbf for black ash, and a bending strength (modulus of rupture) of 15,400 psi for white ash. Wikipedia notes ash is strong and elastic, used for tool handles and, by Fender, as an electric guitar tonewood since 1950. The Handbook's Table 14-1 puts ash heartwood in the slightly or nonresistant decay group, so it is an indoor wood.

Our white ash page shows the end grain, and WoodLens can check bark, a leaf or a cut board from a photo.

Both can look like ridged gray bark from a distance, but the pattern differs:

• Ash - interlacing ridges that form diamond shapes on mature trunks (Colorado State Forest Service).
• White oak - light ash-gray, shallow-fissured and scaly, peeling at the edges of the plates; a little over halfway up the trunk the bark tends to form overlapping scales (Wikipedia).
• Northern red oak - ridges that look like they have shiny stripes down the center; Wikipedia says it is the only tree with that striping all the way down the trunk.

Then check the twigs. Ash branches and buds are opposite; oaks are not on Virginia Tech's short list of opposite-branched trees (maple, ash, dogwood, the honeysuckle family, horsechestnut), so their buds alternate. Oaks carry simple, usually lobed leaves and acorns; ash carries compound leaves and paddle-shaped seeds. See oak leaf identification.

Shagbark hickory is easy to tell from ash, but not every hickory peels. Missouri State University's plant identification page describes mockernut hickory bark as diamond-pattern ridged, the same description the Colorado State Forest Service gives for ash. With bark alone you cannot separate them, so:

• look for alternate buds and branches (hickory) versus opposite (ash);
• look at the buds: Missouri State notes mockernut buds are more orange than those of other hickories;
• look on the ground for nuts in a thick husk (hickory) or paddle-shaped winged seeds (ash).

A photo of the bark plus a twig in WoodLens usually settles it.