Blue Ash

Blue Ash Fraxinus quadrangulataThe blue ash (Fraxinus quadrangulata) is a medium to large-sized tree that is usually 40 to 60 feet tall, but can attain a height of 150 feet with a trunk diameter of 3 feet. It is the only eastern ash with square twigs. The leaves are 8 to 12 inches long with 7 to 11 leaflets, 3 to 5 inches long, oval or lance shaped, and finely toothed margins.

Habitat: Grows on Rocky Bluffs. Found in extreme southeast Iowa.

blue ash tree
Blue Ash Tree - Photo by Richard Webb, Self-employed horticulturist,

Hardiness: Zones 3 though 9

Growth Rate: Moderate to Fast

Mature Shape: Slightly pyramidal, upright with a rounded crown

Height: 40 to 60 feet

Width: 50 to 70 feet

Site Requirements: Native to Iowa, ash trees grow best in full sun and moist, well-drained soils. Ash trees are tolerant of a wide range of soil conditions.

Leaves: Alternate, simple, double-toothed with equal leafbase

Flowering Dates: March - April

Seed Dispersal Dates: September - October

Seed Bearing Age: 25 Years

Seed Bearing Frequency: Every 3-4 years

Seed Stratification: Prechill for 3 months at 40°F

The fruit is 1 1/2 inches long, oblong shaped with a wing to the base of the seed. The bark is gray colored with fissures that seperate scaly or shaggy plates. The inner bark will release a blue dye when crushed and soaked in water - and this is why it is called the blue ash.

Blue ash can be found in southern Ontario, Michigan to southern Wisconsin and southeastern Iowa, south to West Virginia, Alabama, and northeastern Oklahoma. Blue ash are less common than white ash; however, the two can be found together on high quality soil.

blue ash twig
Blue Ash Twig - Photo by Paul Wray, Iowa State University

Diseases that Can Affect Blue Ash

Insects that Can Affect Blue Ash

blue ash bark
Blue Ash Bark - Photo by Richard Webb, Self-employed Horticulturist,