Prickly Ash (Zanthoxylum americanum) Growing & Care Guide for Gardeners
Article by Dean Ravenscroft, Ph.D. - Updated 1st Feb 2024
- Plant Characteristics: A deciduous shrub or small tree with aromatic, compound leaves and prickly stems. Produces clusters of small, greenish flowers followed by reddish-brown berries.
- Growing & Care: Prefers full sun to partial shade and well-drained soil. Tolerant of a variety of soil conditions. Drought-resistant once established.
- Tips for New Gardeners: An interesting addition to USA native plant gardens or naturalized areas. Requires minimal care once established. Handle with care due to the prickly stems.
Zanthoxylum americanum (Syn. Xanthoxyum Americanum) is commonly known as the Toothache tree, Prickly ash, or Prickly-ash.
The plant belongs to the Rutaceae family and is thus closely related to citrus and Rue.
This tree ranges between 15 to 20 feet (4.5 to 6 m) in height and has a spread of 10 to 15 feet (3 to 4.5 m) wide.
Zanthoxylum americanum is a native of Eastern North America. It grows well in US zones 3 to 7, and is thus tolerant of temperatures down to about minus 40 degrees.
zanthoxylum americanum photograph by Manuel.
Its leaf structure is a compound pinnate format with dark green leaves.
The tree blooms with beautiful flowers in the spring, followed by leaf growth. These flowers are a greenish-yellow color and are fragrant.
Ornamental fruits appear on female trees once flowering has completed, reaching maturity in the summer. They have a berry like appearance and are a red-brown color.
It gained one of its common names, the Toothache tree, because of its medicinal properties.
Native Americans would chew the bark or fruits for toothache relief. Other medicinal properties of this tree are associated with fevers, coughs, rheumatism, and external wounds. Bark infusions were also traditionally used to enhance the sense of smell in hunting dogs.
An attractive (one of the few) feature of Prickly Ash is that birds and butterflies (Swallowtail) seek out this tree for protection and as a food source.
The twigs and branches emit a strong lemon peel odor when snapped.
Gardener's HQ Guide to Growing Prickly Ash
New plants can be grown from seeds, root cuttings or from their suckers. To collect seeds, collect the seed capsules, and let dry. The capsules will open and release their seeds upon drying out.
Seeds will require cold weather to germinate, so sow the fresh seeds in the autumn (or stratify them in the fridge).
Zanthoxylum americanum requires full sun for best results but is moderately shade tolerant.
This tree can thrive in droughts as well as moist ravines and thickets.
Prickly ash can tolerate poor soils so long as they are well-drained.
This is not a plant recommended to be grown inside as the needles can reach up to half an inch long.
It is not recommended to grow for ornamental purposes, though it does fairly well when used for hedge rows and screens. As they have sharp thorns they can also be used as a barrier planting.
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Zanthoxylum americanum Growing and Care Guide
- Scientific Name: Zanthoxylum americanum.
- Common Name: Prickly ash.
- Growing Zone: USA: 3 to 07; UK Hardiness H7.
- Life Cycle / Plant Type: Tree.
Plant Details
- Plant Height (Inches): 180 to 300.
- Plant Spread (Inches): 180 to 300.
- Time of Bloom: Summer.
- Flower Details: Green, Yellow.
- Leaf Foliage: Green.
- Fruit:
- Growth Form: Rounded.
Ideal Growing Conditions
- Best Light Conditions: Partially shady to full sunlight.
- Rate of Growth: Medium paced.
- Suitable Soil Types: Acidic, Alkaline, Clay, Loamy, Neutral, Sandy, Slightly alkaline, Well drained.
- Soil Moisture: Moist.
Caring Conditions
- Care:
- Level of Maintenance: Medium.
- Propagation: root suckers.
- How to Prune:
- Pests: No serious problems, can be infesticated by swallowtail butterfly caterpillars.
- Diseases: No serious problems.
Further Information
- Can Attract: Birds, Butterflies.
- Tolerant of: Drought.
- Best Garden Use: Border, En masse.
- Miscellaneous: North American native, Attracts butterflies, Inconspicuous flowers or blooms, Periodic blooms.
- Genus Detail: Zanthoxylum.
- Further Reading and References: Here and Here.
- Family: Rutaceae - The Citrus and Rue Family.
- Closely Related Species: Southern Prickly Ash; Wild Lime; and Flatspine Prickly Ash.
I hope that you enjoyed this guide on how to grow Zanthoxylum americanum. You may also enjoy the following growing guides: How to grow Iris Plants and Agapanthus africanus.
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