Mahonia; Oregon Grapeholly
 

Mature Size, Growth, Longevity

Average mature size of 3-6' tall and 3-5' wide, occasionally to 9' tall in favorable conditions. Tends to sucker, forming colonies. Slow growth rate, 2-3' over 3-4 years. Relatively short lived, 20-50 years.

Native Range

U.S. Native — Native from British Columbia to Oregon. Introduced 1823.

Flower and Fruit Details

Flowers are monoecious, showy, perfect, bright yellow, 2-3" long and wide, slightly fragrant, with a spicy fragrance, borne in terminal racemes, in April, sometimes into May. Fruits are true berries, rounded, dark blue, purplish to blue-black, 0.33-0.5" diameter, July-September. Looks similar to a cluster of small grapes, but not edible for humans.

Leaf and Bark Features

Evergreen: Leaves are evergreen, alternate, 6-12" long, pinnately compound, with 5-13 leaflets, which are stiff and leathery, glossy, dark green. Leaflets sessile, 1.5-3.5" long, spine-tipped, spiny-dentate, with up to 12 teeth per side. Leaves reddish-bronze when emerging, then become dark green. During cold weather of late fall, winter & early spring, leaves turn purplish to bronze, and after a hard winter, browning from desiccation may occur, especially in exposed, windy, sunny sites. Bark is gray-brown, with many shallow, vertical furrows.

Culture and Care

Transplant into moist, well-drained, acid soil. Prefers shade. Zones 5-7. Avoid hot, dry, windy sites to prevent physiological leaf scorch, winter desiccation and browning. Very tolerant of shade, acid or alkaline soils, pH 5.0-8.5, but may get chlorosis in alkaline, high pH soils. Resistant to de-icing salts. Not tolerant of clay soils, flooding or drought. Avoid low, wet areas. Susceptible to leaf rusts, leaf spots and leaf scorch, barberry aphid, scale and whitefly.

Strengths, Weaknesses, Other Facts

Numerous cultivars available. Good wildlife value. 4-season interest: Spring, summer, fall & winter. Hard winters can result in significant desiccation and browning by springtime. Also known by the old name of Mahonia aquifolium.

Suggested Uses

Makes a good shrub border, specimen, foundation plant, or just to brighten a shady area.

Taxa and Plants of this Species at BCA