Feature Tree Archives

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: