Content Detail

Blue ash is very susceptible to the emerald ash borer (Agrilus planipennis) and is not recommended for planting anywhere in this region. It usually requires removal or regular insecticide treatments. Blue ash is a native woodland tree found throughout the Midwest. 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.

To find suitable replacements for this tree, go The Morton Arboretum’s tree and plant finder.  Before purchasing or planting, be sure to check for any local or state guidelines on any selected species, and ensure that this plant is suitable for its habitat by checking its attributes at mortonarb.org or plants.usda.gov.

  • 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

Highly susceptible to the following diseases and pests:

Emerald ash borer

Size:

Blue ash is a large tree growing 50 to 70 feet tall and 25 to 35 feet wide.

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.

List of pests and diseases:

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

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