The Oregon grape (Mahonia aquifolium) is a broadleaf evergreen shrub that grows well in shadier spots. It originated in western North America and is the state flower of Oregon. It will provide color throughout all four seasons with its green and burgundy foliage, yellow flowers, and purplish-blue fruit.
The Latin name given to this species is Mahonia aquifolium, and it is part of the Berberidaceae family. The genus name of Mahonia, which honors American horticulturist Bernard McMahon, is given to this plant, though some botanists believe it should be placed in the Berberis (barberry) genus. Additionally, aquifolium means that the leaves are like those of holly trees and shrubs (Ilex), though they are in a different family.
There are many different common names that are associated with this plant, and they are often used for other species of Mahonia, so specify that you want M. aquifolium to help avoid confusion. They are Oregon grape, Oregon grape-holly, Oregon-grape, Oregongrape, mountain grape, Oregon hollygrape, holly-leaved barberry, tall mahonia, Oregon grapeholly, and Oregon holly-grape. Even though the common names suggest a connection with the fruit, this is not a true grape (Vitis) or in the Vitaceae family.
Hardiness and Growing Tips
The soil needs to be moist with good drainage for optimal growth. It needs to be acidic or at least neutral as alkaline soils can be problematic. Change your soil to be more acidic if the pH is not too much above neutral.
This shrub is best suited for USDA Zones 5-9. It is native to western North America. Partial shade is ideal for this species. It can also be grown in full shade or full sun, though too much light can cause foliage scorching. Try to find a planting location that offers some shelter from the wind. Since these are evergreen and do not drop in the fall, the leaves may dry out in the winter if the shrub is hit by wind often.
Propagation can be performed through the use of seed germination, taking cuttings, and dividing existing plants. The plant will also naturally propagate itself through cloning.
Size and Design Tips
Oregon grape will be 3 to 10 feet tall and 2 to 5 feet wide. Look for the 'Compactum' cultivar if you want a shrub that is shorter, at 3 feet tall. Or, if you want a similar looking shrub that is more of a groundcover, choose the creeping mahonia (Mahonia repens). This species only is about a foot tall at maturity.
The fruit is a berry that does resemble a grape in shape and color. They are edible but are quite tart and can be used to make jams, jellies, and preserves. Oregon grape can be used as part of a wildlife garden to attract butterflies, bees, hummingbirds, and other birds to your yard.
This shrub can clone itself and spread. On one hand, this can be a useful feature as you can use it to populate a native garden or divide to create new plants. However, this tendency can also lead to the species being invasive in some locations. Your local extension service will know if it is a problem in your area.
The evergreen leaves are sharply toothed like members of the holly genus as noted in the species name. It can be used as a privacy screen to keep unwanted visitors out since the leaves are sharp. These are actually pinnately compound leaves that are up to 12" long and made up of several leaflets. When they first appear, they are red. As time passes they turn into a shiny green hue. During autumn, they become burgundy but do not fall off.
In April and May, clusters of cheery yellow flowers appear.
The Oregon grape does tend to form suckers, so pruning can be used to control these to some extent. It is quite tolerant of pruning and can even be cut all the way down to the ground if you want to give it a fresh start, but usually, it is not in need of much trimming. Pruning should be done in spring once the shrub is done blooming.
Pests and Diseases
On this plant, you may find signs of pests such as whiteflies, aphids, or scales. These insects are all likely to leave honeydew, which can lead to sooty mold.
If your planting site receives too much sunlight, the leaves may become scorched. They may also develop chlorosis if placed in alkaline soil. You can sometimes see rusts or leaf spots develop on this shrub.