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Blue ash (Not recommended)

Fraxinus quadrangulata

Common names:
blue ash

Content Detail

Due to emerald ash borer (EAB) susceptibility, blue ash is not recommended for planting 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.

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.

  • 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 (Northern Illinois), Zone 6 (City of Chicago), Zone 7
  • Soil preference Dry soil, Moist, well-drained soil
  • Tolerances Alkaline soil, Clay soil, Dry sites, Wet sites
  • Season of interest early fall, mid fall
  • Flower color and fragrance Inconspicuous
  • Shape or form Irregular
  • Growth rate Moderate
  • Transplants well No
  • Wildlife Insect pollinators, Migrant birds
  • Has cultivars Yes

Native geographic location and habitat:

Blue ash is native from Michigan, south to Arkansas and Tennessee. It can be found in both low, wet sites and dry, upland sites. C-Value: 8 

Bark color and texture:

The bark is gray and broken into a platy texture. It is different from other ashes that are tightly ridged and furrowed.

Leaf or needle arrangement, size, shape, and texture:

The blue ash has compound leaves that are in pairs (opposite), with five to 11 leaflets on each leaf. The leaves are medium green in the summer and change to yellow in the fall.

Flower arrangement, shape, and size:

The spring flowers of the blue ash are perfect (male and female parts in the same flower). They are not ornamentally important.

Fruit, cone, nut, and seed descriptions:

The fruits are winged seeds and somewhat paddle-shaped.

Plant care:

This tree is tolerant of dry sites.  Existing specimens should be treated for emerald ash borer.

List of pests and diseases:

Susceptibility to the emerald ash borer makes the Blue Ash unsuitable for the landscape.

Photo Gallery (5)

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