Shrubs , evergreen, 0.3-3(-4.5) m. Stems usually monomorphic, seldom with short axillary shoots. Bark of 2d-year stems gray-brown or purplish, glabrous. Bud scales 4-8(-14) mm, deciduous. Spines absent. Leaves 5-9-foliolate; petioles 1-6 cm. Leaflet blades thin and flexible or rather rigid; surfaces abaxially glossy, smooth, adaxially glossy, green; terminal leaflet stalked, blade 5.1-8.7(-14.5) × 2.4-4.5(-5.5) cm, 1.7-2.5 times as long as wide; lateral leaflet blades lance-ovate to lance-elliptic, 1(-3)-veined from base, base obtuse or truncate, rarely weakly cordate, margins plane or undulate, toothed, each with 5-21 teeth 0-2 mm tipped with spines to 0.8-2.2 × 0.2-0.3 mm, apex acute or sometimes obtuse or rounded. Inflorescences racemose, dense, 30-60-flowered, 3-9(-11) cm; bracteoles membranous, apex rounded or obtuse, sometimes apiculate. Flowers: anther filaments with distal pair of recurved lateral teeth. Berries blue, glaucous, oblong-ovoid, 6-10 mm, juicy, solid. 2 n = 28, 56. Flowering winter-spring (Mar-Jun). Open woods and shrublands; 0-2100 m; B.C.; Calif., Idaho, Mont., Oreg., Wash. Berberis aquifolium is the state flower of Oregon. It is widely used as an ornamental and has been reported as an escape from cultivation in scattered localities across the continent (Ontario, Quebec, central California, Michigan, and Nevada). Berberis aquifolium is resistant to infection by Puccinia graminis .

Medicinally, various root preparations of Berberis aquifolium were used by Native Americans for stomach trouble, hemorrhages, and tuberculosis; as a panacea, a tonic, a gargle, and an eye wash; and to purify blood. Leaves and roots were used in steam baths to treat yellow fever; karok was used as a poison; and the tips of stems were used to treat stomach aches (D. E. Moermann 1986).

PLANT: Shrubs or subshrubs; wood and inner bark yellow. LEAVES: (in ours) odd-pinnate or trifoliolate, the leaflets thick, evergreen, spiny-toothed, more or less conspicuously reticulate-veined. INFLORESCENCE: racemose to corymbose or umbellate, solitary in the leaf axils or in fascicles; ultimate branches of inflorescence (pseudopedicels) arising from the axils of a single bract; bracteoles 0-2, appressed to calyx or 0-1 cm below it. FLOWERS: yellow; sepals 6 or 9, in 2 or 3 series; petals 6, in 2 series; stamens 6, in 2 series; filaments sometimes bearing 2 teeth at apex; anthers opening by 2 apical valves. FRUITS: few-seeded berries. NOTES: Ca. 500 spp. widely distributed in Eurasia and the Western Hemisphere. All the Arizona species belong to the group often segregated as the genus Mahonia on the basis of compound leaves. Fruits of the members of this genus are edible and often made into jelly. Wood is used in folk medicine since it contains berberine, a compound with antimicrobial properties. A brilliant yellow dye has been obtained from roots and stems. Name apparently of Arabic origin. REFERENCES: Laferrière, Joseph E. 2001. Berberidaceae. J. Ariz. – Nev. Acad. Sci. Volume 26(1).