Mahonia Repens

Oregon Grape

Berberidaceae

The Basics

Creeping barberry, also known as Oregon grape, creeping Oregon grape, creeping mahonia, creeping hollygrape, ash barberry, and dwarf Oregon grape, is an upright to recumbent, evergreen shrub. The stems are solitary, usually unbranched but occur in clonal groups arising from rhizomes. The main root is stiff and deep, and the lateral roots are short and fine. Stem bark is slightly rough and gray brown, and the inner bark is bright yellow, especially the inner root bark. The wood and pith are yellow. The alternate leaves, are pinnately compound with three to seven leathery, sessile, ovate leaflets that are dull on both surfaces, and have spiny-toothed margins. Low in stature and moderately tolerant of shade, creeping barberry is not highly competitive. In Utah, it will not grow in heavy grass and forb stands. It is most frequently seen in rocky or gravely areas with low vegetative cover or under open conifer or hardwood stands with sparse understory vegetation. However, the species is reported to be the dominant understory shrub in closed-canopy Douglas fir in central Idaho. Creeping barberry apparently grows well under conifers that produce a thick layer of decomposing needles. However, it does not flower when growing in shade.The fruits become edible to humans after they have passed through at least one frost. They are used to make jelly, wine, and a juice drink. Native Americans used the berries and the roots for lavender and yellow dyes, respectively, and made teas from the roots to treat a range of afflictions. Creeping barberry contains the alkaloids berberine and oxyacanthin. The species is an alternate host for black stem rust of cereal grains.

Identification

Stem height is 4 to 12 inches (10-30 cm). Each aerial stem arises from a rhizome that gives rise to other aerial stems at intervals. Leaves are pinnately compound with 3 to 7 spine-toothed leaflets. Flowers occur in dense racemes or umbels. Fruits are berries, 0.4 inches long (1 cm) and borne in grape-like clusters. Each berry contains 1 to 4 seeds, 0.2 to 0.4 inches (0.6-1.0 cm) long. Each creeping barberry fruit contains several seeds. Creeping barberry produces 71,120 seeds per pound. Roots: Creeping barberry has fibrous rhizomes and roots that typically grow 0.6 to 2.0 inches (1.5-5 cm) below the mineral soil surface. Rhizomes can sprout from relatively great depth without the stimulus of fire. Bradley found 1 active rhizome branch originating from 5.9 inches (15 cm) below the soil surface that was nearly emergent in Pattee Canyon, in western Montana. In the Black Hills of South Dakota, a 6 ft study plot identified 31 stems originating from the same root system. Roots can reach a maximum rooting depth of 6 feet (1.8 m), providing adaptability to water stress.

Threats

Fire: When fire goes through the area Mahonia repens initially dies from top kill. Once the fire has passed sprouting occurs due to the rhizomes. Mahonia repens also has seeds that occur from onsite and offsite. The seeds are carried over from rodents and birds. The sprouting occurs 4 months after a fires has pasted over and often increases after the 1st year after the fire. 

 Grazers: Mahonia repens contains a toxin called alkaloid which makes it slightly poisonous to livestock, however it is important for wildlife. Bighorn sheep graze Oregon grape during winter months while moose graze it during the fall. Bears rely heavily on the fruit as do birds.

Reproduction

Seeds: Fruits are produced annually from cross-pollinated plants and the seeds from those fruits are dispersed from birds and mammals. Regeneration comes from seed banks but have not been studies in the wild. In warehouse conditions the seeds can be stored for 5 years. Viable seeds have been found 10 seeds in 0 to 2 in layer. 

 Germination: For the seeds to have germination needs of stratification. Mahonia repens requires cold stratification for 1 to 3 months. 

 Sprouting and growth: From the rhizomes Mahonia repens can sprout from a fire. It also can sprout from layering. The growth of Mahonia repens is rapid after disturbance but slow when growing over a long period of time. Stems can live for 10 years and generally die due to lack of sunlight.

Species Distribution

Citation

FEIS
Ulev, Elena D. 2006. Mahonia repens. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/shrub/mahrep/all.html [2021, March 29].

USDA Plants Database
USDA, NRCS. 201. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
Distribution Map photo credit and Tubnail photo credit