Oregon grape plants are colorful western shrubs with year round appeal and chances are there’s a species that will fit into your Pacific Northwest landscape. Named after Bernard McMahon, an Irish-born American nurseryman, the genus Mahonia is a member of the barberry family (Berberidaceae). But you may also see Oregon grape classified as Berberis, indicative of the extensive debate among botanists on how to classify this species. Although included in the large genus Berberis (an alteration of the Medieval Latin barberis, or barberry, from Arabic barbārīs), Oregon grape is still known as Mahonia in most commercial horticulture, so either is correct (at least as far as I’m concerned!). 

Wildlife value
Like all native plants grown where they evolved, Oregon grape plants are extremely beneficial and attractive to wildlife. Flowers provide for pollinators like bees, moths, butterflies, and hummingbirds, while the fruits, which may remain on the plant into winter, are favorites among birds such as towhees, robins, and waxwings, as well as mammals. Some butterfly and moth species rely on Oregon grape plants to host their larvae, including the brown elfin butterfly. Year round cover may support arthropods, birds, reptiles, amphibians and small mammals.

Three species
You can’t go wrong with tall Oregon grape (Mahonia aquifolium) for an evergreen, erosion-controlling, woody-stemmed, slightly prickly screen, barrier or woodland border, as part of an unpruned hedgerow, or as an accent plant (pictured top). Aquifolium means “water leaf,” likely named after the lustrous, wet-looking surface of the plant’s leathery leaves that Lewis and Clark first noticed near the Columbia River. Introduced to Britain in the 1820s as an expensive ornamental, its holly-like, pinnately compound leaves begin a bronzy coppery color, then mature to a deep green, with orange, red, or purple highlights in very sunny or cold conditions. Dense clusters of showy golden-yellow, lightly fragrant flowers appear in early to late spring. Ripening in late summer, the dusty-blue, round to oblong berries are slightly reminiscent of grapes, hence the name. Although they are tart and have large seeds, they are suitable for jams and jellies (with beaucoup sweetener) and have traditional medicinal properties, as do the roots. 

Tall Oregon grape’s range includes most of western Washington and Oregon, parts of Idaho and much of California, as well as northeastern Washington and southern B.C. It can handle nearly full sun to shade, but being a woodland species often found growing in somewhat open forests, it prefers some shade (although very deep shade will result in fewer flowers and fruit). Though it does best in slightly moist, acidic, well-drained soil, it’s an undemanding plant that can handle many soil types and drought when established. However, it is intolerant of poorly drained soils and high water tables. Since it will gradually spread into a thicket via tough rhizomes, place it away from pathways and allow it to eventually spread into a wildlife protective clump. If you don’t plan for its growth or it somehow gets out of hand, roots may be occasionally pruned and stems may be cut (as seldom as possible) nearly to the base for renewal. Arching stems typically reach four to eight feet in height, sometimes on the lower end in garden situations.

Try growing it with trees and shrubs such as Douglas-fir, western hemlock, ponderosa pine, vine maple, Indian plum, oceanspray, serviceberry, salal, and smaller companions like sword fern, western columbine, fleabane, delphinium, and others.    

Cascade (or long leaved) Oregon grape (Mahonia nervosa) is another handsome plant, but this one grows only up to about three feet tall, often lacks shiny leaves, and very slowly spreads into a lovely, evergreen, soil-stabilizing ground cover over many years. Nervosa means “having distinct veins or nerves” and refers to the leaf venation. Showy, fragrant, erect, pale to bright yellow flowering stalks, which put on their show in early to mid spring, are trailed by the familiar deep blue berries in late summer to fall. 

This species naturally occurs in moist to dry forests, at low to mid elevations mainly west of the Cascades including Vancouver Island, often with oceanspray, osoberry, vine maple, sword fern, salal, and oxalis, but it’s also an associate of the drier Oregon white oak and madrone habitats. It prefers shade to part shade in moist, acidic soil, but can handle drought in cool areas when established. It’s a nice substitute for invasive English ivy.

Low (or creeping) Oregon grape (Mahonia repens) is an evergreen ground cover that grows one to two feet tall and four to six feet wide. It has a large range in the west; in Washington and Oregon it is mainly found east of the Cascades growing in conifer forests, so it does well in dry, shady conditions but can take some sun. Its leaves (pictured below) may be glossy or dull, tend to be rounder and—though toothed—feel less prickly than tall Oregon grape. In nature, where its range sometimes overlaps with tall Oregon grape (and in garden situations where we often place plants that don’t belong together), it may hybridize with its cousin and produce plants that are a bit taller than the true species. 

 

 

 

 

 

 

Propagation 
All Oregon grape species are best grown from seed (without drying them), with at least three months of cold stratification outdoors (wet, pre-chilled seed may also be planted in spring). Seed germination is reportedly erratic and unpredictable. If you have established plants you may find their progeny beneath them or elsewhere, as seeds are dispersed by birds and mammals; anything but very small transplants may not survive. Cuttings may also be tried in late fall. 

As always, buy plants propagated from source material that originated as close as possible to your site. Using such “local genotypes” helps ensure that you get plants that are well adapted to your area and that genetic diversity—which helps plants (and animals) adapt to changing conditions—is preserved. Ask growers and nurseries about their sources if you’re unsure.

Do you have Oregon grape but aren’t sure which species you have? This page has a handy leaf comparison (see photo on lower right column).
 
 
© 2019 Eileen M. Stark

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