fbpx Prickly-ash | The Morton Arboretum


Dark green compound leaves of prickly-ash

Prickly-ash is a tall, colony-forming small tree or large shrub reaching 15 to 25 feet tall and wide. Twigs and stems are covered in 1/2 inch prickles making it difficult to use in the landscape.  In spite of its common name, it is not  related to Ash trees (Fraxinus spp.) of the Olive family. Rarely found in the nursery trade. 

"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:

Zanthoxylum americanum

All common names:

Prickly-ash, Prickly ash, Pricklyash, Toothache tree

Family (English):


Family (Botanic):


Tree or Plant Type:

  • Shrub,
  • Tree

Native Locale:

  • Chicago area,
  • Illinois,
  • North America

Landscape Uses:

  • Hedge,
  • Massing

Size Range:

  • Small tree (15-25 feet),
  • Compact tree (10-15 feet),
  • Large shrub (more than 8 feet)

Light Exposure:

  • Full sun (6 hrs direct light daily),
  • Partial sun/shade (4-6 hrs light daily)

Hardiness Zones:

  • Zone 3,
  • Zone 4,
  • Zone 5 (Chicago),
  • Zone 6,
  • Zone 7

Soil Preference:

  • Moist, well-drained soil,
  • Wet soil


  • Dry sites,
  • Occasional drought,
  • Wet sites,
  • Occasional flooding,
  • Alkaline soil,
  • Clay soil

Seasons of Interest:

  • late summer

Flower Color & Fragrance:

  • Inconspicuous

Shape or Form:

  • Multi-stemmed,
  • Thicket-forming

Growth Rate:

  • Moderate

More Information:

Size & Form

A large colony forming shrub to small tree reaching 15 to 25 feet tall and wide.

Tree & Plant Care

Prefers full or partial sun and moist to dry soils. This shrub can adapt to light shade, but it may fail to produce flowers and fruit.
Different types of soil are tolerated, including clay-loam, and rocky material.
Difficult to find in the nursery trade.

Disease, pests, and problems

No serious pests or diseases.

Disease, pests, and problem resistance

Tolerant of black walnut toxicity.

Native geographic location and habitat

C-Value: 3
Forms thickets in moist wood edges and areas and along stream banks.
In drier sites it is located on rocky slopes.

Bark color and texture 

Twigs are brown and smooth, while young shoots are light green and nearly glabrous to pubescent.
Pairs of stout prickles up to 1/3" long are scattered along the branches, twigs and shoots; these spines are somewhat flattened and curved. 

Leaf or needle arrangement, size, shape, and texture

Alternate, dark green, compound leaves reach about 6-12 inches long and develop along the twigs and young shoots.
Leaflets are finely toothed with a yellow gland between each tooth.
Small prickles run along the rachis (stalk) and petiole.
Crushed leaves smell like citrus.

Flower arrangement, shape, and size

Dioecious. Male and female flowers on separate plants.
Yellowish-green flowers appear before the leaves in clusters along last years twigs.

Fruit, cone, nut, and seed descriptions

Fruit is a red, small, 2-valved capsule that  splits down the middle to reveal a shiny black seed.


Location of Zanthoxylum americanum (Prickly-ash) at the Arboretum