Green Ash (Fraxinus pennsylvanica)

A deciduous tree from the Olive Family (Oleaceae)

Green Ash, one of the most common and rapidly growing woodland trees in Ohio, is also a popular shade tree for urban areas, well-known for its adaptability to almost any site.

One of the first trees to change color and drop its leaves in autumn, it is native to eastern and central North America, where it is found primarily in floodplains, cut-over forests, and abandoned fields.

It grows to about 60 feet tall by 40 feet wide when found in the open, with a medium to rapid growth rate. Its shape is upright oval when young, becoming upright spreading to upright rounded with maturity. In addition, its lower branches become both pendulous and upswept with age. As a member of the Olive Family, Green Ash is related to the other Ashes, as well as the Fringetrees, Forsythias, Privets, and Lilacs.

Historically, Green Ash was once considered a variety of Red Ash. The old Red Ash was distinguished by the ruddy fuzziness on its leaflet undersides and stems, and for the tendency of its fall foliage to have traces of a burgandy or red color. The old Green Ash had leaf and stem features that were smooth. Now, these two types of Ash are considered as one, and are collectively called Green Ash.

Planting Requirements - Green Ash is very adaptable to a wide range of soil types (organic, clay, sandy, or rocky), soil pHs (acidic, neutral, or alkaline), and moisture levels (wet, moist, or dry). It is noted for being extremely tolerant to many types of environmental stresses (summer heat, reflected light, sweeping winds, drought, flooding, poor soils, compacted soils, high pH soils, winter salt spray, winter salt deposition, and air pollution). It grows in full sun to partial sun, and is found in zones 3 to 9.

Potential Problems - Among the common ash trees, Green Ash is generally the most healthy. This is why it is overplanted as a street tree and shade tree in urban areas (only the seedless male cultivars are sold as landscape trees today). However, borers and scales are still occasional pests, while leaf anthracnose and trunk canker are occasional diseases. In addition, seed litter from female trees, surface roots (with age in compacted or shallow soils), and storm damage at maturity due to easily splittable wood with weak crotch angles are potential liabilities, primarily in urban areas.

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 Green Ash are opposite, pinnately compound, and have 5 to 9 leaflets (usually five or seven).

The leaflets have either no stalks, or very short stalks attached to the central rachis.

Leaflets are medium green to dark green in color, and are often finely serrated on the upper half of their margins.

Green Ash is so named because the color of its leaves is green on both the upper leaflet surfaces and the lower leaflet surfaces, and because its autumn coloration often has a lot of green in it.

Fall color occurs in very early autumn, and is usually green-yellow, but can be golden-yellow in good years.

Other Identification Features

Male flowers and female flowers occur on separate trees of Green Ash (a dioecious species) in late winter or early spring.

Both types of flowers occur before the leaves emerge and often go unnoticed, since they are small and do not have petals. (Photo of White Ash flower shown above for representation).

Fruits (also known as samaras) hang in clusters from female trees of Green Ash, with each fruit being composed of a thin anchoring seed attached to a narrow wing.

The individual samaras of the ashes spin downward when they fall from the tree.

When the leaves of Green Ash fall in autumn, they leave behind D-shaped leaf scars on the twigs (right side of image), where the "D" is laying on its side.

This is directly compared to the U-shaped leaf scars found on the twigs of White Ash (left side of image). In either case, a lateral bud lies above the leaf scar.

The young bark of Green Ash is usually flaky (as shown in top image), and forms tall interlacing ridges and deep furrows with age (as shown in bottom image), yielding a classic diamondback pattern on the mature bark.