Colorado Tree Coalition Committee and Program Feature Tree Autumn Purple Ash

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Autumn Purple Ash

Common Name: Autumn Purple Ash

Scientific Name: Fraxinus americana ‘Autumn purple’

Family: Oleaceae

This Tree in Colorado:

Growth Rate, Form and Size: Is a fine selection of pyramidal to upright round form. It will grow to a height of 60ft and a width of 45ft.

Landscape Value: Autumn purple ash is best suited for medium-sized spaces or large spaces, like a park. A small space is not recommended as this can stress the tree and cause a poor-developing root system. Also, it would not be a good tree to set under power lines, as it will grow to a height of 60ft.

Zones: 3 to 9

Fruit: A 1 to 2” long samara with it’s width about ¼”. No ornamental color or quality to the fruit.

Flowers: This tree is dioecious or possibly polygamo-dioecious. Both sexes appear in a panicle before the leaves emerge. The corolla absent, with the color being green to purple and blooming in April.

Foliage: Leaves are opposite and pinnatley compound, 8 to 15” long, with 5 to 9 leaflets, stalked, 2 to 6” and 1 to 3” wide. Body is ovate-lanceolatle, with acute to acuminate at apex. Usually the margin is remotely serrated. Summer color is dark green and glabrous on the surface with a pale green under the leaf surface. The fall color is a reddish purple that normally lasts 2 to 4 weeks.

Bark: gray-brown bark is very smooth in youth, but becoming very deeply furrowed and ridged in just a few short years, with the ridges interlacing to form a diamondback pattern of 2" thick bark at maturity.

Insect and Disease Problems: This tree can have many problems if poorly cared for. It is susceptible to: Cankers, Lilac/ash borer, carpenter worms, and ash flower gall. Recently, the ash sawfly has become a big problem on Autumn purple ash up and down the Front Range of Colorado, chewing leaves in May and June. Ash borer is a big problem in Colorado where ash trees grow.

Information Sources:

Dirr, Michael “Manual of Woody Landscape Plants: Their Identification, Ornamental, Characteristics, Culture, Propagation and Uses”. 1990

Ohio State University's Plant Dictionary

Contact Information

Colorado Tree Coalition
P.O. Box 270968
Fort Collins, CO 80527-0968

Phone: 970-491-6303