Prickly ash flower

Other names and notes

Trees and Shrubs of the Eloise Butler Wildflower Garden
The oldest public wildflower garden in the United States






Zanthoxylum americanum Mill.
Rue (Rutaceae)
Flowers Late April to May; Red fruit in July

(Common Prickly-ash, Northern Prickly Ash, Toothache Tree). 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 shrub. The wood is a light brown or deep yellow color. The bark is dark brown with good sized prickles (6mm and up to 13mm 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 to brown. Buds are are red and woolly. Leaves are alternate, oddly pinnate of usually 5 to 11 ovate leaflets on very short stalks, dark green above and lighter under with light fine hair when young. Fall color is a mellow yellow. The inflorescence is a tight cluster of unstalked 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 3.5mm wide. Male flowers have 4 or 5 yellowish-green short erect petals and 4 to 5 stamens, but no calyx. Female flowers 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 dryer 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 best kept on the edge. 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." is for Philip Miller, Scottish botanist (1691-1771) who was chief gardener at the Chelsea Physic Garden and wrote "The Gardener's Dictionary".

Prickly Ash twig Prickly ash flowers Prickly ash trunk
Above: Flowers form on the old wood at each node of the twig, opening before the leaves. Above: Male flower detail - 4 or 5 petals and no calyx with 4 to 5 stamens. Female flowers have 2 to 5 pistils. Above: Bark of a main stem. Prickles are evident there also.
Below: Seed development
Prickly Ash new berries
Prickly ash green fruit
Above: The female flowers beginning to mature into seeds.
Above: Full size green fruit 2 months after flowering
Below: The shrub with mature seed capsules in Late Summer Below: The capsules split open to release a single black seed
Prickly Ash Berry seeds
Leaves and twigs
Prickly ash leaf Full plant
Above: The pinnate leaf with an odd leaflet number. Below: Nice yellow autumn color. Right: A young plant about 6 feet high.
Prickly ash fall leaf
Below left: Spring twig: The thorns of Prickly-ash are paired at the nodes. Below right: The buds are covered with red hair and are quite visible in autumn above the leaf scar.
Prickly ash twig Prickly ash twig

Notes: Prickly-ash is indigenous to the Garden area. Eloise Butler recorded it on April 29, in her first plant survey of 1907. Many times thereafter she would note planting some new species in the "prickly ash arbor". It was present in the Garden at the time of Martha Crone's 1951 Garden census and on later census lists. The western range of Prickly ash in North America is the Dakotas, Nebraska, Missouri, Oklahoma on a north/south line and from there eastward to the coast excepting only Mississippi in the south and Manitoba in the north. In Minnesota it is found in almost all counties except the far northern tier and the arrowhead. A few scattered exceptions elsewhere. It is on the endangered list in 4 eastern states.

Medicinal uses: There is a fair amount of literature on the historic medicinal use of this plant. The root, bark and berries are the official ingredients, having been listed in the U.S. Pharmacopoeia. Bark infusions were used for treating skin problems, swollen joints, back pain, fevers and more. Crushed root was used to treat fever. Bark poultices were used for rheumatism and sharp pains. Infusions of the berries were used to treat hemorrhage, as a cough syrup or to treat other issues. The common name "toothache tree" comes from the use of the bark, beaten or powdered, and packed around an aching tooth. In Minnesota, Densmore (Ref. #5) in her study of the Minnesota Chippewa, reported on two uses: A decoction of the root was used internally for quinzy and swelled throat (also taken as a gargle); second, a decoction of the root was used as a bath to strengthen the legs and feet of a weakly child, especially if the limbs were partly paralyzed. See Hutchins (Ref #12) and Mrs. Grieve(Ref. #7) references for more information.


References: Plant characteristics are generally from sources 32, W2, W3, W7 & W8 plus others as specifically applies. Distribution principally from Wi, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.  
©2013 Friends of the Wild Flower Garden, Inc. All photos and text are by G. D. Bebeau unless otherwise credited. "" 110114