   Oregon Grape and its Native Relatives - August 12, 2009 Jeff Schalau, Associate Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County Oregon grape (Mahonia aquifolium) is a common landscape plant that somewhat resembles holly in its rich green color and spiny leaves. However, it is far more suitable for landscape use in the southwest than holly. Oregon grape has a few native relatives growing in the high plains, canyons, and mountains of north central Arizona. It is also resistant to wildlife herbivory and has moderate irrigation requirements making it worthy of consideration for your landscape. Oregon grape is an evergreen shrub growing from upright stems produced by a slow spreading rhizomatous root system. It's neither a grape nor a holly but a member of the barberry family (Berberidaceae). In protected spaces with regular irrigation, it can reach 5 to 6 feet in height. Oregon grape has compound leaves with 7 to 13 leaflets, each ringed with spiny teeth. Most of the year leaves are dark green, but in winter they turn bronze to bright red and persist on the plant. Its yellow flower clusters bloom in spring and are followed by the formation of raisin-sized bluish fruit. Oregon grape is most effective in mass plantings where it can form a moderately dense hedge. It will look its best in light shade or on a northern/eastern side of a structure or fence. As it grows taller, the lower stems will often be bare. In dense stands, the bare lower stems will be hidden by younger shoots. Oregon grape should never be sheared. Rejuvenation pruning can be used to remove older stems and promote new shoots. Oregon grape’s spininess can also be used to advantage where you want to discourage people from taking shortcuts through landscaped areas. Oregon grape is native to the Pacific Northwest and was collected during the Lewis and Clark expedition. Neither Lewis or Clark were well trained in plant science, so prior to the expedition, President Jefferson sent Meriwether Lewis to Philadelphia for a crash course in botany from Dr. Benjamin Smith Barton. While there, Barton introduced him to Bernard M'Mahon, a Philadelphia nurseryman and friend of the president. Lewis learned how to properly collect and save seeds from M'Mahon, and following the expedition, seeds of many plants were successfully propagated. This included Oregon grape which M'Mahon sold through his catalog. Mahonia was named after M'Mahon. The most popular Oregon grape cultivar is dwarf Oregon grape (Mahonia aquifolium ‘Compacta’) which resembles regular Oregon grape but is half as tall and quicker to spread by rhizomes. This is a good choice for smaller spaces where a mass of shiny, dark green foliage is desired. A local native, creeping Oregon grape (Mahonia repens), closely resembles M. aquifolium but has smaller leaves and wider leaflets. Creeping Oregon grape only grows to about 8 to 12 inches when grown with limited irrigation. It also spreads by rhizomes and makes an excellent shade-tolerant ground cover. It is found throughout the west including rocky canyons in local mountain areas. Fremont barberry (Mahonia fremontii), also called algerita, is a large drought-tolerant shrub common to the grasslands, chaparral, and pinyon/juniper woodlands of northern Arizona. It can reach a height of 10 feet and a width of 8 feet. The flowers and berries closely resemble those of Oregon grape. However, the foliage is blue green and the leaves are smaller and very spiny. Red barberry (Mahonia haematocarpa) looks very similar to Fremont barberry, but is generally smaller in stature. While the flowers look similar to other Mahonia species, the ripe fruits are red rather than blue. It also has similar foliage in color and texture, but the terminal leaflet is distinctly longer than the other leaflets. Both Fremont and red barberry are available through specialty nurseries that handle native and drought-adapted plants. The roots, stems, and berries of various Mahonia species have been used by Native Americans and modern day herbalists for a variety of treatments/ailments. Mahonia contains berberine (also found in goldenseal). The bluish berries are used to create a natural lavender dye and the bright yellow roots and inner bark are also used to create yellowish dye. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |