green ash in autumn

Green Ash Trees

Green Ash trees are tall trees, which can grow anywhere from 65 to 120 feet tall.  One easy way to narrow down the identification of a Green Ash tree is that the branches grow opposite of each other, which is unusual in trees. The gray bark also has a distinctive X pattern visible on it.

The leaves grow on leaf stalks, with 7-9 leaves arranged opposite each other on the stalk, and with one at the end. This is referred to as pinnately compound.

Scientific Name and Plant Family Information

The Scientific name for the Green Ash tree is Fraxinus pennsylvanica. All Ash trees are in the Fraxinus genus, and the pennsylvanica means from Pennsylvania.

It is in the plant family Oleaceae (Olive), which also includes olive trees in the Mediterranean along with privet, forsythia and lilac shrubs. 

An interesting thing about this family is that the plants generally lose their leaves in the winter in northern latitudes (deciduous) and are evergreen in the South.

gray bark showing x pattern
Bark pattern on Green Ash tree

Through the Seasons

In the spring, the trees produce seeds that have a wing and carry them away on the wind. In the fall, the leaves turn gold.  In the winter, these tall, straight trees can be recognized by the X shapes on the bark.

group of trees in early fall
A Green Ash tree is the tallest tree in this group of trees along a drainage ditch

Native or Non-Native?

Although the Green Ash is native in Eastern Colorado along the edges of creeks and lakes, in this location, it is not a native.

It has been planted widely in cities to provide shade, replacing the Elm trees that were killed by the Dutch Elm disease and the wind carries the seeds to nearby locations where they sprout easily.

These trees are very adaptable as they tolerate drought, wind and alkaline soil and can grow rapidly.

Where to find in Willow Spring Open Space

Green Ash trees can be found along the bike path on the east side of the Willow Spring Open Space where a drainage ditch comes in and creates a wet environment.

Did You Know?

Green Ash trees are very susceptible to several insect problems, including an insect known as the emerald ash borer which is native to Asia and has been spreading across the nation. If there is an infestation, the emerald ash borer will typically kill an ash tree within 3 to 5 years after infestation.

References and Further Reading

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