A Plant for All Seasons
Common Name: Oregon Grape Holly
Botanical Name: Mahonia aquifolium
Form: upright, broad, spreading
Plant Type: broadleaf evergreen shrubs
Mature Size: 3ft to 10ft x 5’
Origin: North & Central America, Asia, Himalayas
Hardiness Zone: 5 to 9
Foliage: dark green to bronze, turn purple in winter in direct sun, 6x 2.5 cm, pinnately compound, lobed with sharp spine at lobe tips, stiff, leather-like
Flowers: clusters (racemes) of fragrant yellow trumpet shaped flowers with 6 yelllow petals surrounded by 6 yellow sepals.
Fruit: hanging clusters of blue edible berries
Exposure: prefers shade to partial shade, but tolerates sun
Soil: prefers moist, well-draining, acid soil, tolerates most soils, including wet ones
Uses: screen, fillers, shade gardens, mixed borders, privacy hedge, attracts birds and butterflies
Propagation: cuttings in summer into autumn
Pruning: not necessary, but if needed do so in spring once the danger of frost has passed
Problems: rust and powdery mildew but it’s not common
Oregon grape hollies are used extensively by municipalities, landscapers and developers because of their versatility, toughness, winter interest, soil and shade tolerance and low maintenance. However, they are not as popular with maintenance crews because the spines on their holly-like foliage, which makes them painful to touch and to prune. Mahonia grape holly is also indigenous to the Pacific Northwest and is used in native and wildflower gardens.
The popularity of mahonias is shared throughout the world, although they mostly originate from North America. They are easy to grow, and they look good all year long. Their attractive form, leaf colour and flowers stand out when other plants are dormant during the winter. Throughout the autumn through winter, the many clustered spikes of fragrant, bright yellow blossoms are framed by their deep green to purple leathery, holly-like foliage. It’s a lovely display, especially on grey days. The flowers also attract butterflies and birds.
Their dangling clusters of purple berries resemble clusters of grapes, hence their common name. Although they are edible, they are tart therefore are often used to make jam. Please note that their active compound, berberine, is unsafe for pregnant, nursing women and children. The highest level of berberine is in the seeds, so remove them before making jam and consuming the berries. Wait for frost to harvest the berries for the best flavour. The berries attract juncos, towhees, waxwings, robins and other birds.
Dyes are also made from the mahonia. The berries are used to make blue, purple, pink or green dye depending on the pH of the soil and water. The stems and roots also produce a yellow dye often used by indigenous peoples of the Pacific Northwest.
Although mahonias are soil tolerant, they prefer moist, good draining soil and benefit greatly when mulched. Protect them from full sun and exposure to high winds.
Pruning: Remove or cut back wayward stems to reshape plants in spring after the last frost. At the same time, deadhead, and prune out any diseased, damaged and dead stems. Remove old, non-productive as well as spindly branches. For leggy mahonias that just have growth at the top of bare stems, cut some or all of the branches back by ¼. After pruning water well and mulch.
Propagate: Take cuttings in late summer into early autumn from healthy new growth from the current season. For more on semi-hardwood cuttings click on Taking Cuttings.
Cultivars and varieties: