Hardiness zones:
Sunset 8-24
USDA 7-11
Landscape Use: Landscape entryways, foundation and group plantings, natural light atriums, shaded courtyards and patio gardens
Form & Character: Oriental, stiff and upright, informal, rugged
Growth Habit: Highly variable, very stiff, rigid, and upright, 3' to 6' in height. Spreads very slowly by underground creeping rhizomes.
Foliage/texture: Persistent leaves are alternate and pinnately compound, 6 to 12" length. Leaflets are 2 to 3" length, lanceolate, sometimes with undulating margins and sharply spined teeth along their margins, dark glossy green adaxial, thick, waxy cuticles, and pale green abaxial, arranged 5 to 9 per leaf. Lateral leaflets are opposite and sessile, while the terminal leaflet has a petiole; each leaflet has a distinct midrib. The young foliage and new stems are brightly colored red and purple. Winter foliage is reddened by cold weather. Oregon grape has a medium coarse texture.
Flowers & fruits: Edible yellow flowers are monoecious, perfect, small borne in long, upright racemes. Fruit are small (3/16") drupes, waxy green when immature and dark blue, edible (sour) when mature.
Seasonal color: Yellow flowers in spring, berries in summer and fall
Temperature: In Phoenix, Oregon grape like people suffers mightily when temperatures exceed 110oF.
Light: Partial to full shade is imperative to successfully cultivating Oregon grape in Phoenix. NO western exposures.
Soil: Tolerant of all soils conditions except high alkalinity and salinity
Watering: Needs regular supplemental water during the warmer months (like June when it's blazing hot in Phoenix) of the year.
Pruning: Prune as needed, can even prune to ground after bloom to reinvigorate growth.
Propagation: Seed, semi hardwood shoot or root cutting, division of basal clumps much the same as Nandina domestica.
Disease and pests: In moist temperate climates mahonias are predisposed to numerous leaf bacterial and fungal (rust, mildew) diseases as well as insects with rasping mouth parts. In drier climates, one would never know this as mahonias seem generally indestructable.
Additional comments: The genus Mahonia is named after Bernard McMahon, an early American horticulturist of the 18th and 19th centuries. There are many cultivars (such as 'Compactum' and 'Golden Abundance') and hybrids with M. pinnata (California grape) such as the named hybrid 'Ken Hartman'. My personal favorite Mahonia is the cultivar of Mahonia pinnata called 'Skylark' (from Suncrest Nurseries Inc. in California) which has 6" leaves that are dark green with a highly polished surface, brilliant red in new growth and purple-tinted in winter.
Both the roots and rhizomes of Oregon grape have been used medicinally for hundreds of years to treat infections because of their powerful antibiotic properties. The plant contains the alkaloids berberine and hydrastine. Berberine is highly bactericidal, amoeboidal and trypanocidal. Oregon Grape extracts were shown in one pharmacological study to reduce inflammation (often associated with psoriasis), and to stimulate the white blood cells known as macrophages. The roots are used in herbology as a nutritional aid to the digestive and circulatory systems. The fruit is an excellent gentle and safe laxative.
A yellow dye is obtained from the inner bark (cortical region) of all stems and roots and dark green, violet and dark blue-purple dyes are obtained from the fruit. A green dye is obtained from the leaves.
Mahonia repens (creeping mahonia) is a creeping and spreading dwarf (to 1', but generally less) that is native to montane and alpine regions of the western United States including Arizona. It is used along with Oregon grape as a landscape plant (sparse ground cover) in higher elevation Arizona landscapes in the Flagstaff, Prescott, Payson and Show Low/Pinetop areas.
