Trees & Shrubs of the Eloise Butler Wildflower Garden

Prickly-ash is a native tall shrub, growing to 25 feet in height, with a trunk of up to 6 inches in diameter, but the plant is usually much shorter, growing as a multi-stemmed understory shrub. The wood is a light brown or deep yellow color.

The bark is dark brown with good sized prickles (6 mm and up to 13 mm long) that are flattened on the sides and somewhat curved. These appear in pairs along the twigs and branches at nodes with the buds.

Twigs are aromatic with a fragrance of lemon peel when crushed. They are light green initially, turning to reddish-brown in the Autumn, then to brown. Buds are red and woolly and appear above the old leaf scars.

Leaves are alternate, oddly pinnate with usually 5 to 11 ovate leaflets on extremely short stalks, dark green above and lighter under with light fine hair when young. The leaflets just back from the three-some at the tip are the largest. Fall color is a mellow yellow contrasting with the reddish Autumn color of the new twig.

The inflorescence is a tight cluster of un-stalked flowers appearing on the previous season's wood. They open before the leaves. Most plants are dioecious, that is, with male and female flowers on separate plants.

Flowers are greenish-yellow, about 3 to 3.5 mm wide. Male flowers (staminate) have 4 or 5 yellowish-green short erect petals and 4 to 5 stamens, but no calyx. Female flowers (pistillate) have 4 to 5 short erect petals, yellow green also, 2 to 5 pistils and no calyx.

Fruit: Fertile flowers mature to a capsule, (a follicle), turning from green to reddish-brown in the autumn. The capsules split open when mature and the single black oily seed (sometimes two) emerges.

Habitat: Prickly-ash grows in woods and thickets and tolerates some shade and drier upland soils. It has a suckering habit which will create dense stands, but no insect or disease problems. The flowers and later the red fruit give it landscape interest, but the plant is best kept on the edges of your landscape.

Names: The genus name, Zanthoxylum, comes from xanthos and xylon meaning "yellow wood." The species, americanum, is 'of America.' The author name for the plant classification - ‘Mill.’ refers to Philip Miller, Scottish botanist (1691-1771) who was chief gardener at the Chelsea Physic Garden and wrote "The Gardener's Dictionary” which ran through 8 editions. He was considered “the accurate Miller,” the most famous gardener and nurseryman of the day. The book spread the idea of gardening among the middle class who could now enjoy what was formerly the province of the wealthy. His prime source for North American plants was John Bartram. The name 'toothache tree' is explained below.

Comparisons: When the twigs are bare, the stout prickles may be mistaken for a young Black Locust, Robinia pseudoacacia, except that the Locust has hidden buds, not red exposed buds. After leaf out the flowers and seed capsules of the two species are entirely different.