by Marilee Henry
As we transition into spring, the brilliant yellow flower clusters of tall Oregon-grape will soon be wafting their honey-scented fragrance into the air, attracting hummingbirds and a multitude of other pollinators. Last spring, I watched in wonder at the parade of "bugs" feasting at my stand of tall Oregon-grape, including early-hatching Orchard Mason bees. Being among the year's first native bloomers, this plant is a critical source of nectar and pollen for many native insects. It also is a host plant for the Brown Elfin and other butterfly and moth larvae that are such an essential food source for birds in raising their young.1
We have three species of Mahonia2 in Washington, all of which are evergreen woody shrubs and wonderful choices for urban landscaping. Low Oregon-grape (M. nervosa), growing to ~3 feet, is found mostly in the western part of the state as an understory forest component that prefers shade and tolerates more moisture, while creeping Oregon-grape (M. repens) grows mostly on the eastern slopes of the Cascades in sunnier, drier conditions with a more trailing form reaching about 2 feet in height. Tall Oregon-grape (M. aquifolium) is found at low elevations on both sides of the Cascades, commonly in open woods to sagebrush slopes, from southern B.C. to northern California, and as far east as Montana. In form it is erect and stiff-branched, with alternate compound leaves made up of 5 to 9 opposite glossy spiny-toothed leaflets. It prefers sun and good drainage but tolerates partial shade and can grow in most soil types. In sun its height reaches 6 to 8 feet; in shade it can be taller but more spindly.
The differences between the compound leaves and flower clusters of the Mahonia species are shown on this website3. Leaves of tall Oregon-grape are distinguished from low Oregon-grape in having glossier leaflets tops, fewer leaflets per leaf (5 to 9 vs 9 to 19), and a prominent central vein with smaller veins spaced along the central one running to the leaflet margins (pinnately veined), vs 4 to 6 main veins radiating along the length of the leaflet from its stalk (palmately veined). M. repens is also pinnately veined, but is less glossy, has more spiny teeth per leaflet, and has tiny, raised bumps on the leaflet undersides. English holly, sometimes confused with tall Oregon-grape, is easily identified by its single (non-compound) leaves spaced alternately along its stems.
Besides being a great evergreen backdrop for many garden elements, tall Oregon-grape adds beautiful hues to the landscape with pinkish-bronze coloring in its new spring growth and variable red to purple coloring to its leaves in winter. It can be used to form thick hedges for privacy and/or for sheltering birds and other wildlife by spacing individual plants 5 feet apart. Clusters of bluish round fruits resembling small grapes ripen in fall and are eagerly eaten by many birds and mammals. Though sour when raw, they are reputed to make delicious jams and wines!4 The flowers are also edible and have been made into a honey-flavored beverage and sorbets. Blue and yellow dyes have been made from its berries and the inner bark of its stems respectively.
Tall Oregon-grape is best propagated from seed, but needs cold stratification to break dormancy. Seeds should be cleaned and planted outside in fall or stored in the refrigerator for 3 months before planting in spring. Softwood cuttings in spring may also be attempted. This species does not have good success when salvaged as large plants. However, once established, new plants will slowly spread by rhizomes which can be dug up and transplanted in fall.
Remember, "You are nature's best hope!" - Doug Tallamy, author of "Nature's Best Hope" and "Bringing Nature Home".
Marilee Henry
Kirkland Community Wildlife Habitat Team Member, Washington Native Plant Society (WNPS) Native Plant Steward, Green Kirkland Steward, Finn Hill Neighborhood Alliance Contributor
Read this excellent article on native plants for bird population stability at https://www.ecolandscaping.org/10/landscaping-for-wildlife/wildlife-habitats/a-chickadees-guide-to-gardening-how-to-create-habitat-for-birds-in-urban-settings/
There is debate over which genus to assign to the Oregon-grape species. Some references use Mahonia, and some use Berberis. I am using both scientific and common names employed by the U.W. Burke Herbarium https://burkeherbarium.org/imagecollection/results.php?Terms=mahonia&x=0&y=0&Type=Names
NativePlantSalvage.org site shows compound leaf and flower cluster comparisons between our 3 native Mahonia species at https://www.nativeplantsalvage.org/blog/the-native-amp-native-adjacent-mahonias-why-we-love-all-four
Oregon-grape jam recipes, including mixing with blackberries http://s158336089.onlinehome.us/OregonGrapeJam/OregonGrapeJam.html
We're happy to answer questions about Kirkland's Community Wildlife Habitat Program, and engage in related discussions, by email kirklandcwh@ilanga.com. Please forward this article to interested contacts, and let us know of addresses to add to our e-news list.
Sincerely,
Kirkland Community Wildlife Habitat Team
Aly, Ann, Kent, Launa, Marilee, Sharon
Kirkland's Community Wildlife Habitat Program strives for each person to make our community healthier for people and wildlife. We encourage residents to certify their properties to show support for wildlife-friendly activities: https://www.nwf.org/certifiedwildlifehabitat
Appreciating and enhancing habitat in Kirkland, which is situated on the ancestral, unceded land of the Puget Sound Salish people; we acknowledge and honor the land with gratitude.
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