Berberis aquifolium (formerly Mahonia aquifolium) is among the tallest of an informal subgroup within Berberis known commonly as the Oregon grapes (note: not actually grapes). This upright-growing species can sometimes exceed 4.5m (15 ft.) in height, and hence Berberis aquifolium is commonly known as tall Oregon grape or tall mahonia.
Tall Oregon grape can be found growing in dry forests, rocky outcrops, and shrublands from southern British Columbia to northern California, and east to Montana and Idaho.
Like all of the former Mahonia species, the leaves are pinnately compound. Five to eleven ovate glossy-green leaflets are margined by sharp spines, much like English holly leaves (Ilex aquifolium). The sweetly-fragrant yellow blossoms appear in January locally, when their bright colour very much contrasts with our typical grey winter sky. Tall Oregon grape may continue flowering until May. Arranged in tightly-packed racemes, the hermaphroditic flowers can be either self-pollinated or insect-pollinated. Berberis aquifolium blossoms are the state flower of Oregon.
By late summer, the blossoms are replaced with clusters of deep blue spherical berries. These berries are 6-10 mm (to ~0.5 in.) in diameter, and appear to be coated with a whitish bloom. They taste more tart than sweet, but they are very much edible and I think juicy and nice enough to eat out of hand. When cooked, their flavour is compared to that of black currants.
Tall Oregon grape has a rich ethnobotanical heritage. In Food Plants of British Columbia Indians, Part 2/Interior Peoples (British Columbia Provincial Museum, 1978), Nancy Turner notes that regional indigenous peoples have long eaten the berries fresh or mashed into cakes that are then dried. According to Plants of Southern Interior British Columbia, edited by Roberta Parish, Ray Coupé, and Dennis Lloyd (Lone Pine, 1996), the Okanagan, Nlaka’pmx, Secwepemc and St’at’imc peoples of southern interior British Columbia have known for quite some time that the berries can be made into jelly. This preserve is often used as an accompaniment to meats; recipes to make the jelly can be found online. Traditional medicines made from the roots were/are used to treat tuberculosis, hemorrhaging, and stomach ailments; to purify the blood; to improve digestion; and to wash eyes. The stem tips have a traditional use of soothing stomach aches. A steam bath infused with the roots and leaves was used to treat yellow fever, but that disease is now rarely a concern in North America. Finally, tall Oregon grape has use as a dye plant: the bright yellow inner bark and roots yield a yellow to green dye, the leaves yield a green dye, and the berries yield a dye that is dark purple-blue to dark green.
Berberis aquifolium was introduced to Europe in 1823 (Parish, Coupé, Lloyd), where it was cultivated as an ornamental. Several hybrids and cultivars have have been recognized with the Royal Horticultural Society’s Award of Garden Merit, including Berberis × wagneri ‘Pinnacle’ (a hybrid of Berberis aquifolium and Berberis pinnata) and Berberis aquifolium ‘Apollo’.