Feature Tree – October 2005
Single Leaf Ash
(click here for Tree of the Month archives)

Family: Singleleaf Ash, Fraxinus anomala (Oleaceae family)  

Habit:  Tree has a round habit as a young tree becoming more upright and elliptical in form.     Commonly found in the draws and canyons of western Colorado and southern Utah where more water will collect because of run off or storm events

Hardiness:  Zone 5 to 7    

Leaves:  Unlike the typical green ash which has a pinnately compound leaf the singleleaf ash has mostly simple leaves on the stem.  Leaves are smooth, glossy and slightly toothed on the leaf margin.  The bright green leaves will turn a brilliant yellow color in the fall.  From a distance this tree is striking because of its yellow fall color.         

Twigs:  On young branches light tan in color turning gray with maturity.   Twigs are slightly 4-angled when young.      

Bark:  As the main trunk matures the bark becomes dark brown to gray and is slightly furrowed. 

Flowers:  Small and light green in color growing in clusters.  They are not showy. 

Fruit:  Winged seed is a samara up to three quarters of an inch in length.  Hang on the tree in clusters.  Seeds mature in mid-summer and can persist on the tree through the winter.    

Landscape Value:  Not commonly found in the nursery trade at this time.  This tree has great potential for Colorado’s xeric landscapes because it is tolerant of heat, drought and high pH soils.  The current national champion is growing in a red sandstone amphitheater south of Gateway, Colorado.   

Diseases/Insects:  No observed pests in its native habitat. 

Information Sources: 

            Trees of Utah and the Intermountain West, Michael Kuhns

Fire Effects Information System, USDA Forest Service  http://www.fs.fed.us/database/feis/index.html