The essential guide for oregon grape growers, or anyone whoever wants to grow oregon grape.
• Mahonia aquifolium
• (Muh-HO-nee-uh ak-wih-FO-lee-um)
• Family Berberidaceae
• Hardy evergreen shrub
Good autumn leaf color, abundant clusters of yellow flowers, and blue-black, edible fruits have made this handsome, spiny-leaved evergreen shrub a widely promoted ornamental, especially in the American West. Less well known are its coloring and medicinal properties, which have long been used by Native Americans and others.
The genus Mahonia comprises seventy species of evergreen shrubs and small trees native to North and Central America and Asia. It was named for the Irish-born Philadelphia nurseryman Bernard M’Mahon, or McMahon (1775–1816), whose American Gardener’s Calendar (1806) was America’s first comprehensive, practical gardening book.
M. aquifolium is native to western North America from British Columbia to Northern California but is planted throughout much of the country. It grows to about 6 feet tall and 3 to 5 feet wide and spreads by suckers.
The glossy leaves are pinnately divided into five to thirteen leaflets, each of which resembles a holly leaf (aquifolium, which means “sharp-leaved,” is the Latin name for holly). Red-bronze when newly open, the leaves become dark green in summer, then purplish or bronze in fall and winter, particularly when planted in sun and where winters are cold.
The dense clusters of tiny flowers, which appear in March through May, are 2 to 3 inches long and slightly fragrant; they’re Oregon’s state flower. Grapelike berries 1/3 inch in diameter ripen in July through September and are the source of the plant’s common names, Oregon grape holly and Oregon holly grape.
Oregon grape may be used as a foundation planting, specimen shrub, or in a woodland setting. Hardy in Zones 4 or 5 to 8, it’s best grown in the shade in hotter climates and with protection from leaf-scorching winter winds in colder ones. ‘Compacta’ is a 2-foot-tall cultivar with foliage that starts out glossy light green and turns to a dull green in summer. For a ground cover, try 10-inch-tall creeping mahonia (M. repens), which has dull blue-green leaves in summer and smaller “grapes.” A number of other American and Asian mahonias are sold as landscape plants.
The fruits are high in vitamin C and have been used to treat and prevent scurvy, but the bitter roots and root bark are the parts usually used in medicinal preparations. Native American medicine men prescribed them to stimulate the appetite as well as to treat ulcers, heartburn, rheumatism, and kidney and skin disorders. White settlers learned about these uses and invented more of their own: a nineteenth-century remedy for hemorrhage and jaundice was made by steeping the roots in hot beer. The alternative common name yerba de sangre (“blood herb”) testifies to its use as a blood purifier. It is mildly laxative.
Much of Oregon grape’s current use seems based on tradition or on limited studies of its primary active ingredient, the alkaloid berberine, which is also found in other Mahonia species, barberry and goldenseal. Berberine stimulates the flow of bile, supporting its use to improve gall bladder function, and kills bacteria and amoebas, which seems to support its use in Asia to treat diarrhea. Oregon grape is high in antioxidants, compounds that neutralize the cell-damaging free radicals implicated in many diseases. A study showing that alkaloids found in Oregon grape slowed division of certain skin cells, together with its antioxidant activity, suggest its usefulness for treating psoriasis, a chronic inflammatory disease characterized by overproduction of skin cells.
At least one veterinarian is prescribing a tincture of Oregon grape root for treating urinary tract infections in cats and dogs.
The flowers are used to make a sort of lemonade. The acid, slightly bitter fruits are sweetened and cooked into pie fillings, jellies, and jams. Wine can be made from the juice of the fruits. The roots, twigs, and leaves yield a yellow dye. The fruits yield shades of brown with various mordants, but the colors are not lightfast. The wood is used to make small carvings.
Oregon grape prefers well-drained, humus-rich soil and a spot in the shade, but it will tolerate less-than-ideal conditions. Established plants need little water except in the South. Shape plants by pruning long stalks out at the base and removing unwanted suckers.
The species may be propagated from seeds. Fresh seeds (with the flesh removed) germinate readily. Chilling for three months in moist planting medium enhances more rapid germination. Keep the seedlings in a nursery bed for a year, then transplant to their permanent locations.
To propagate cultivars, either divide entire plants, dig up some of the suckers, or root stem cuttings taken in summer or fall (dip the lower ends in rooting hormone). Any of these methods may also be used to increase your stock of the species.
The herb’s typical pests include rusts, aphids, scales, and whiteflies.
A looper caterpillar that sometimes disfigures the leaves can be tamed by applying the biological control Bacillus thuringiensis. Chlorosis (yellowing of the leaves) may occur in alkaline soils and probably indicates the need for a plant that’s better adapted to those conditions.
Harvest the roots in late fall or early spring.
• Forestfarm, 990 Tetherow Rd., Williams, OR 97544-9599. (541) 846-7269; fax (541) 846-6963. Catalog $4. Plants of Mahonia aquifolium, M. aquifolium ‘Compacta’, M. repens, and several other Mahonia species and hybrids.
• Heronswood Nursery Ltd., 7530 NE 288th St., Kingston, WA 98346-9502. (360) 297-4172; fax (360) 297-8321. Catalog $5. Plants of M. aquifolium and several other Mahonia species and hybrids.
• Horizon Herbs, PO Box 69, Williams,OR 97544-0069. (541) 846-6704; fax (541) 846-6233. Catalog $1. Seeds of M. aquifolium.
• Richters, Goodwood, ON, Canada L0C 1A0. (905) 640-6677; fax (905) 640-6641. Catalog free. Dried root of Mahonia aquifolium.
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