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Zanthoxylum americanum

northern prickly ash

Rutaceae Central and eastern North America

Attracts Pollinators Attracts Butterflies Deer Resistant Drought Tolerant Fragrant (moderate)

Native to North America

SunFull Sun – Part Shade

WaterMedium · drought-tolerant

HardinessZones 3–7

Overview

Zanthoxylum americanum is a deciduous, suckering shrub or small tree in the citrus family, reaching 10-25 feet (3-7.6 m) tall and forming dense, thicket-like colonies. The stems and branches bear paired, sharp prickles, and the pinnately compound leaves, 5-10 inches (13-25 cm) long with 5 to 11 leaflets, release a citrus-like scent when crushed. It is dioecious, with separate male and female plants; in early spring, before or as the leaves emerge, both sexes produce small clusters of tiny yellow-green flowers along the previous year's twigs. Female plants follow with clusters of small red, pitted fruits that split to reveal shiny black seeds, both aromatic and pungent. Native to central and eastern North America, it grows in woods, thickets, fencerows, and along streams on a range of soils. Z. americanum tolerates shade, varied soils, and cold, but its prickly stems and strong suckering make it spread into broad colonies that are hard to contain. Chewing the bark or fruit produces a numbing, tingling sensation, the source of the name toothache tree.

Native Range

Native to central and eastern North America, from Quebec and Ontario south to Georgia and west to the Great Plains. It grows in woodlands, thickets, fencerows, and streambanks on a wide range of soils.

Suggested Uses

Used in naturalized plantings, wildlife and butterfly gardens, hedgerows, and erosion control on banks, where its suckering habit forms a dense thicket. As a host for the giant swallowtail and a nectar and fruit source, it suits habitat-focused plantings, spaced 6-10 feet (1.8-3 m) apart or allowed to colonize. Its prickly stems also make it a barrier or security planting.

How to Identify

Recognize it by paired sharp prickles on the stems, pinnately compound leaves with 5 to 11 leaflets that smell of citrus when crushed, and clusters of tiny yellow-green flowers set close to the twigs in early spring before the leaves expand. Female plants bear small red, dotted fruits that open to shiny black seeds. The prickly stems, citrus scent, and numbing bark together identify it.

Appearance

Size & Dimensions

Height10' - 25'

Width/Spread10' - 20'

Reaches mature size in approximately 7 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~3 weeks

Spring

Flowering occurs in early spring, generally April to May, before or just as the leaves unfold. The small yellow-green flowers form tight clusters along the older wood and are easy to overlook. Male and female flowers are on separate plants, so only female plants set the red fruit that ripens in late summer.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

loam clay sand rocky

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

5-8 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grow Z. americanum in full sun to partial shade in moist, well-drained soil, though it adapts to dry and poor ground. It is cold-hardy and needs little care once established. It spreads aggressively by root suckers, so it forms wide colonies unless the suckers are removed. Both male and female plants are needed for fruit. The sharp prickles make handling and pruning difficult. It has few serious pests and serves as a larval host for the giant swallowtail butterfly.

Pruning

Pruning is done in late winter while dormant, cutting out crowded or damaged stems and removing root suckers to limit the colony. The prickles make pruning slow, and protective gloves reduce injury from the spines. The plant resprouts readily from cut stumps and roots.

Pruning Schedule

winter