Blue ash (Not recommended)

Summer foliage of blue ash.

Due to susceptibility to emerald ash borer (EAB), blue ash is not recommended for planting anywhere in this region and usually requires removal and/or replacement. Blue ash, a Midwest native, is often found growing in limestone outcrops. It has distinctive, 4-sided winged stems and gray platy bark. Currently, ash trees cannot be sold in Illinois. Check with your state for quarantine restrictions.

This species is native to the Chicago region according to Swink and Wilhelm's Plants of the Chicago Region, with updates made according to current research.

Botanical name:

Fraxinus quadrangulata

All Common Names:

blue ash

Family (English):

Olive

Family (Botanic):

Oleaceae

Tree or Plant Type:

  • Tree

Foliage:

  • Deciduous (seasonally loses leaves)

Native Locale:

  • Chicago area,
  • Illinois,
  • North America

Size Range:

  • Large tree (more than 40 feet)

Mature Height:

50-70 feet

Mature Width:

25-35 feet

Light Exposure:

  • Full sun (6 hrs direct light daily)

Hardiness Zones:

  • Zone 4,
  • Zone 5 (Chicago),
  • Zone 6,
  • Zone 7

Soil Preference:

  • Dry soil,
  • Moist, well-drained soil

Acid Soils:

  • Tolerant

Alkaline Soils:

  • Tolerant

Salt Spray:

  • Moderately Tolerant

Soil Salt:

  • Intolerant

Drought Conditions:

  • Tolerant

Poor Drainage:

  • Moderately Tolerant

Ornamental Interest:

  • Fall color,
  • Persistent fruit/seeds,
  • Attractive bark

Season of Interest:

  • Early fall,
  • Mid fall

Flower Color & Fragrance:

  • Inconspicuous

Shape or Form:

  • Irregular

Growth Rate:

  • Moderate

Transplants Well:

  • No

Wildlife:

  • Insect pollinators,
  • Migrant birds

More Information:

Tree & Plant Care

This tree is tolerant of dry sites.

Disease, pests, and problems

Susceptibility to the emerald ash borer makes this tree unsuitable for the landscape.

Native geographic location and habitat

C-Value: 8

Found in both low wet sites and dry, upland sites.

Bark color and texture 

Bark is gray and broken into a platy texture (different from other ashes that are tightly ridged and furrowed).

Leaf or needle arrangement, size, shape, and texture

Compound leaves are in pairs (opposite), with 5 to 11 leaflets on each leaf.
Leaves are medium green in summer, changing to yellow in fall.

Flower arrangement, shape, and size

The flowers of this species of ash are perfect (male and female parts in the same flower). Not ornamentally important.
Flowers appear in spring.

Fruit, cone, nut, and seed descriptions

Fruits are winged seeds (somewhat paddle-shaped).

Location of Fraxinus quadrangulata (Blue ash (Not recommended)) at the Arboretum