ODNR Division of Forestry Blue Ash

America's forestry movement actually started in Ohio with the creation of the American Forestry Association in Cincinnati in 1875.


Lisa Bowers, (614) 728-4210
Program Administrator

Division of Forestry
2045 Morse Rd.
Building H1.
Columbus, OH 43229

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Blue Ash (Fraxinus quadrangulata)

A deciduous tree from the Olive Family (Oleaceae)

4-7
40'
80'
slow
full sun
part shade
narrow upright
to upright rounded
alkaline soils
adaptable

Blue Ash, present almost exclusively in the western half of Ohio, is the ash tree that is different in four respects from other Ashes found east of the Mississippi River.

First, it usually has square rather than round, young twigs that may be winged or corky. Second, its mature bark is usually scaly and platy rather than ridged and furrowed. Third, it does not have separate male and female trees, since all of its flowers are "perfect", and therefore every tree can yield fertile seeds under appropriate conditions. Fourth, the pioneers extracted a blue dye from its inner bark, giving it the common name of Blue Ash.

Like Green Ash and White Ash, the high-quality and slightly more dense wood of Blue Ash is harvested to make tool handles, furniture, and for use as firewood. However, its fall color is the poorest, being pale yellow to green in most years.

A native of midwestern North America, Blue Ash is often found at limestone outcrops and therefore thrives in dry soils of alkaline pH. It may grow to 80 feet tall by 40 feet wide, with a slow growth rate. Its shape is narrow upright when young, becoming upright rounded with maturity. As a member of the Olive Family, Blue Ash is related to other Ashes as well as the Fringe Trees, Forsythias, Privets, and Lilacs, plus the namesake of the family, the Olive Tree.

Planting Requirements - The preference of Blue Ash to alkaline soils (that is, those of high pH) accounts for its primary distribution in western Ohio, where the glaciated soils tend to be "sweet", rather than "sour". It often occurs at limestone outcrops, where the underlying rock gives the subsoil and topsoil a higher pH. Blue Ash adapts to a variety of stresses, especially to poor, dry, rocky soils. It grows in full sun to partial sun, and is found in zones 4 to 7.

Potential Problems - Like other ash trees, Blue Ash is occasionally susceptible to borers and scales as pests, and leaf anthracnose and trunk canker as diseases. In addition, seed litter from all trees and surface roots (with age in compacted or shallow soils) are potential liabilities in urban areas. Since it is slower-growing than most other ashes, storm damage does not occur as frequently, as its wood is more dense and stronger.

Emerald Ash Borer(Agrilus planipennis), is a destructive exotic pest from Asia. This metallic wood-boring beetle attacks all of Ohio's native ash species, and has no known significant natural enemies in this country. EAB has been discovered infesting ash trees in Michigan, Ohio, Indiana, and Illinois. The first Ohio discovery was in Lucas County in February of 2003.

Leaf Identification Features

Leaves of Blue Ash are opposite, pinnately compound, and have 7 to 11 leaflets which are often narrow.

Five wide leaflets are shown at left, demonstrating the genetic diversity of all species.

The leaflets may have margins that are smooth, finely serrated, or noticeably toothed. The leaf undersides often display a fuzziness along the midrib of each leaflet.

When the leaves drop in autumn, they leave behind small D-shaped or U-shaped leaf scars on the twigs, with a small lateral bud resting above each scar. Fall color ranges from green to pale yellow.

Other Identification Features

Blue Ash has perfect flowers, defined as those that have both male (pollen-bearing) and female (ovule-bearing) structures within the same flower. Thus, every Blue Ash tree has the potential to bear fruits (known as samaras), unlike most ashes that have separate male and female trees.

A wide wing extends along the length of the fruit, and may be either rounded or notched at its apex. The anchoring seed of the fruit is rather flat as compared to Green Ash or White Ash.

Blue Ash is unique among the ashes in the four-sidedness of its young twigs, and often has distinct lines, corkiness, or wings at each of the four edges.

This trait disappears as the twigs become small branches, and may be absent altogether on some trees.

The light-gray bark of Blue Ash is usually scaly to platy, and takes on a distinct shingled appearance with age. This is in striking contrast to most other ashes, which are usually composed of interlacing ridges and deep furrows, giving them a diamondback appearance.

In some cases, the mature bark does have flat-topped ridges that barely interlace, rather than a shingled appearance.