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Ash (Fraxinus spp.) Identification

Fraxinus spp. Characteristics

Hosts Ash trees (Fraxinus spp.) are the only known North American hosts of EAB. Ashes have pinnately compound leaves arranged opposite one another on the branch. Each leaf bears 5-9 leaflets. The fruit is a winged seed (samara). Some ash species have bark with interlacing ridges that form a diamond-like pattern when mature.  Identification of Emerald Ash Borer.
Once-Compound Leaf
ash leaf
 		 Oppositely Arranged
leaves arranged opposite
 
Fruit/Seed (samara)
Green Ash Fruit
 Bark of White Ash
White Ash bark

Some Non-hosts of the EAB That Could Be Confused with Ash

  • Box-elder (Acer negundo) has pinnately compound leaves with opposite arrangement, but only 3-5 leaflets per leaf that are somewhat more coarsely toothed.
  • Hickories (Carya spp.) and walnuts (Juglans spp.) have pinnately compound leaves with alternate arrangement.  
  • Buckeye (Aesculus spp.) leaves are arranged oppositely, but are palmately compound (leaflets radiate from a single point). 
  • Maple (Acer spp.) and dogwood (Cornus spp.) leaves are oppositely arranged but are simple rather than compound.

Resources

Michigan State University Extension Bulletin "Distinguishing Ash from other Common Trees." (4 pp, .pdf)

MSU Extension Site: Ash Tree Identification Guide
 
 
Division of Forestry Shield


Florida Department of Agriculture and Consumer Services