Scientific: Mahonia aquifolium (According to many taxonomists the current scientific name is Berberis aquifolium with the genus Mahonia now being relagated to synonym status. However, I happen to love the old genus name Mahonia, thus I'll hang onto it as my own 'personnally accepted' scientific name for a while longer)
Common: Oregon grape
Family: Berberidaceae
Origin: Moist coastal canyons and valleys of northern California, western Oregon (state flower of Oregon) and Washington as an understory ground cover. Oregon grape has naturalized in Great Britain where it has been loved and cherished in landscape gardens for years.

Pronounciation: Ma-hon-EE-a a-qui-FOL-ee-um

Hardiness zones:
Sunset 8-24
USDA 7-11

Landscape Use: Landscape entryways, foundation and group plantings, natural light atriums, shaded courtyards and patio gardens. Mahonia will grow in Phoenix and Tucson with western sun protection, but thrives as a landscape plant in higher elevation Arizona cities such as Prescott, Payson, Cottonwood, Sedona, Show Low, and even Flagstaff.

Form & Character: Oriental, stiff and upright, informal, rugged.

Growth Habit: Highly variable, very stiff, rigid, and upright, 3 to 6 feet in height. Spreads very slowly by underground creeping rhizomes.

Foliage/texture: Persistent leaves are alternate and pinnately compound, 6 to 12 inches in length. Leaflets are 2 to 3 inches 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: Yellow flowers are monoecious, perfect, small borne copiously on long, upright racemes, edible. Fruits are small 3/16 inch 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 and eggs suffer mightily when temperatures exceed 110oF. Conversely, Oregon grape foliage turns a wonderful reddish color during winter when the weather is cold such as in Flagstaff.

Light: Partial to full shade is imperative to successfully cultivating Oregon grape in Phoenix. This means absolutely NO western exposures.

Soil: Tolerant of all soil conditions except high alkalinity and salinity. Of special note, all mahonias do exceptionally well in heavy clay soils.

Watering: Mahonia needs regular supplemental water during the warmer months (like June when its blazing hot in Phoenix) of the year.

Pruning: All Mahonia plants are pruned just like Nandina (heavenly bamboo) which means prune canes (stems) back (heading cuts) individually to different lengths as needed to promote a full canopy of leaves. One can even head back (prune) Mahonia severely to the ground after bloom to reinvigorate growth.

Propagation: Seed, semi-hardwood shoot or root cutting, division of basal clumps much the same as Nandina domestica, micropropagation. I used to successfully propagate Mahonia plants in landscapes along the central California coast by direct sticking stem cuttings into the ground in a shaded garden spot during the later fall months.

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 (like southern California and Arizona, 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 hybrid cultivar of Mahonia aquifolium and Mahonia pinnata called 'Skylark' (cross made by M. Nevin Smith in Watsonville, CA). This 'ubber boss' cultivar I first planted in the early 1980s when I was a young dude landscape contractor in central California. It has mature leaves that are dark green with a highly polished surface, brilliant red to orange new leaves and stems and can become purple-tinted in response to winter cold.

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 foot tall, 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 the Show Low/Pinetop areas of eastern Arizona.