Mahonia (Oregon Grape)
Mahonia is a genus of spiny-leafed, evergreen shrubs in the Berberidaceae family that includes approximately 70 species, the majority of which come from the temperate zones of East Asia, the remaining from North and South America. Many species are simply called mahonia.
Some botanists maintain that the name of the North American Mahonia species remain unchanged and label than as Mahonia, while others lump them into the Berberis genus.
- Noted differences between berberis and mahonia plant groups include:
- Spineless stems of Mahonia have many small pinnate leaflets—similar to a feather’s structure— and differ markedly from the barberries that generally have simple spiny, individual leaves not divided into leaflets.
- Mahonias are evergreen while berberis species may be evergreen, semi-evergreen, or completely deciduous.
- Mahonia species develop blue or black berries while berberis berries are more commonly shades of red or purple, rarely yellow.
- However they are classified, an estimated thirteen Mahonia species are California natives, prized for their handsome foliage, panicles of fragrant yellow flowers, large, leathery leaves with toothed margins, and miniature grape-like berries.
Selecting a Mahonia
- Care must be taken when selecting Mahonia plants for the home garden since some attain large, awkward size in maturity.
- A few are quite shrubby, while others are branched, single-stemmed, and form expanding colonies; and still others are groundcovers.
- The California natives described here are extremely drought-tolerant once established; Asian species require moderate water.
- Several Chinese species lend themselves to sites where drama or an architectural statement is the foremost feature.
- Examples are bealei and M. lomariifolia that have very long arching, prickly leaves with many leaflets on tall plants that often reach 10 ft. high and wide.
Commonly Planted Species
California native plant nurseries may list the following Mahonia species as a Berberis species, but home gardeners continue to call them mahonias.
- Mahonia aquifolium (Oregon grape) is one of the best known of the native mahonias, ascending as single stems or an erect shrub 3-7 ft. tall.
- Rhizomes travel below ground to form dense clumps. Their spread may be difficult to control.
- Foliage is leathery, dark green, and spiny, often copper-colored in spring and darkening purple or maroon depending upon exposure to sun and/or cool temperatures.
- Yellow flowers provide nectar for hummingbirds; blue berries feed robins, finches, and towhees, and also make a delicious jelly.
- ‘Compacta’ grows 1-2 ft. tall, spreading up to 5 ft. wide or more with age and commonly used as an attractive ground cover or low foundation planting.
- Mahonia nevinii Nevin’s mahonia develops into a 6-12 ft. tall, 8 ft. wide shrub with rigid arching stems.
- Pointed leaflets open metallic grey and mature to soft blue-green.
- Yellow-gold flowers bloom profusely in spring, followed by an abundance of red-orange berries.
- This native mahonia has adapted well to Bay Area gardens. In the wild, it is fairly rare and is listed as an endangered species.
- Mahonia nervosa, called longleaf mahonia, grows in colonies of stiff, single stems with leathery leaves 1½ -2 ft. long divided into 20 or more dark green, red-veined leaflets that deepen to burgundy in winter.
- Fragrant clusters of yellow flowers and frosted dark purple berries complete the form and texture.
- This low-growing woodland shrub can be used as a ground cover that somewhat resembles a leathery fern.
- Mahonia pinnata is native to coastal bluffs and scrubby inland woodlands along the Pacific Coast to Oregon.
- This species is valued for its crinkled, wavy, holly-like foliage that emerges with copper and reddish tints.
- Young shrubs are fairly compact, 4-5 ft. tall, before spreading via underground runners, sending up more thick stems to form a colony up to 15 ft. high.
- ‘Golden Abundance’ is even taller and wider and produces an abundant crop of large golden flowers followed by bluish-purple berries.
- ‘Ken Hartman’ and ‘Skylark’ are superior selections for their more compact growth 5-6 ft. or somewhat taller.
- Mahonia repens, creeping barberry, is considered one of the prettiest mahonias when its blue-green leaves turn metallic bronze or soft rose in winter.
- It is another low 1-3 ft. shrub highly valuable as a cover for rocky terrain or slopes as it creeps by underground stems.
- In sunny sites, short, dense clusters of yellow flowers precede globular blue berries that attract birds. In shade, this mahonia does not bloom.
- No supplemental water is usually required in shaded situations once plants are established. Irrigation is helpful inland during intense heat spells.