Berberis nervosa

Berberis nervosa, commonly known as dwarf Oregon-grape, Cascade barberry, Cascade Oregon-grape, or dull Oregon-grape, is a flowering plant native to the northwest coast of North America from southern British Columbia south to central California, with an isolated population inland in northern Idaho. It is especially common in second growth, Douglas-fir or western redcedar forests, making use of those pools of sunlight that intermittently reach the ground.

The plant was collected by Lewis and Clark during their famous expedition to the West before being described for western science by Frederick T. Pursh in 1813.

Description
It is an evergreen shrub with short vertical stems, mostly less than 24 in, while the leaves reach higher, rarely up to 7 ft tall on exceptional sites.

The leaves are compound and of opposite arrangement, with 9–19 leaflets; each leaflet is strongly toothed, reminiscent of holly, and somewhat shiny, but less so than tall Oregon-grape. The leaflets do not have a single central vein as in that species, but several veins arranged fan-like, branched from the leaflet base, hence the epithet nervosa.

The flowers bloom from early to late spring and are similar to those of other Oregon-grapes, forming small yellow flowers in erect clusters up to 8 in in length.

The fruits are dark-blue, globose berries of .3 in in diameter which occur in clusters and are tart-tasting.

Taxonomy
Berberis nervosa was scientifically described and named by German-American botanist Frederick Traugott Pursh in 1813. In 1818 Thomas Nuttall placed it in the new genus Mahonia as Mahonia nervosa. A paper was published by Joseph Edward Laferrière in 1997 summarized the arguments in favor of Berberis as the correct classification. As of 2023 most botanists place the entire genus Mahonia within the genus Berberis including Plants of the World Online (POWO) and World Flora Online.

Ecology
Low Oregon-grape thrives in sun or shade and is a common or dominant species throughout the understories in montane, sub-montane, and mixed evergreen forests in the Pacific Northwest. It reaches greatest abundance on relatively dry and warm sites, but occurs in fairly moist environments as well. It grows in a variety of soil types. It is restricted to lower elevations, from sea level to 6000 ft.

Berberis nervosa can complete its life cycle even in the deep shade of dense hemlock-western redcedar forests, so it is a climax species in old-growth forests where it is often dominant. It also occurs in disturbed sites, usually reaching peak abundance from 4 to 10 years after fire or clearcutting.

The plant can reproduce via seeds or by vegetative means, sprouting from rhizomes which extend laterally through the soil.

Its foliage is browsed by black-tailed deer and Roosevelt elk in some areas, but is ignored in others. Various small mammals feed on the foliage extensively, and it is extremely important food source for the white-footed vole in the Coast Range of Oregon. The fruits are eaten by small birds and mammals, and by black-tailed deer in some areas. The nectar of the genus Berberis is favored by the Anna's hummingbird.

Uses
Some Plateau Indian tribes drank an infusion of the root to treat rheumatism. Modern medicine uses it against parasites, bacteria, viruses, diabetes, and high cholesterol.

The Yana people dried and ground the fruits to make a mush. They can also be dried and eaten like raisins, or used for jelly.

The inner bark is colored yellow by the alkaloid berberine, and was used as a dye by native groups.

The leaves are often used in floral arrangements.