MAHONIA. North and Central America, Asia. Certain botanists tell us these all properly belong in Berberis. However, they are almost universally known by their older name, which may yet rise again. These are rugged evergreen shrubs, often creeping by underground rhizomes to form broad colonies. All have leathery leaves divided lengthwise into pairs of toothed or spiny leaflets. They bear clusters of yellow flowers which develop into decorative, usually dark blue berries, often showing a waxy “bloom” like real grapes.
Most mahonias prefer full sun near the coast, light shade inland, reasonably well drained soil, and moderate to little watering when established. Watch for and control the small loopers (a type of caterpillar) which attack and skeletonize the leaves. Hardiness varies.
aquifolium. Oregon grape. The best known of the group, these are 3-6’ shrubs native to California and Oregon. The stems are lined by large, shiny, dark green leaves, usually bronzy in new growth. Many 3" sprays of flowers are clustered at the shoot tips in spring, forming sweet, edible berries in summer. We grow the typical form from seed. ‘Compacta’ is a dwarf selection, clumping profusely and seldom over 3’ tall. It has tightly packed leaves and typical flower clusters. 0oF. or below.
‘Golden Abundance’. This impressive cultivar was introduced in the 1970s by Rancho Santa Ana Botanic Garden, but has been surprisingly slow to capture the public fancy. It remains a valuable selection. It shows its hybrid vigor in its sturdy, well branched trunks and large size. The plant can easily reach 8’ in height and twice that in breadth. The leaves are 6-10" long, with several broad, thick, deep green leaflets. Masses of bright yellow flowers adorn the plant for several weeks in spring, followed by clusters of purple berries.
nervosa. Longleaf mahonia. A forest native, quite distinct from other mahonias. It grows slowly, eventually making loose colonies of solitary stems, each usually 1’ or less high. The leaves can be 1’ long or more and made up of up to 20 satiny, deep green leaflets. These take on a beautiful purple cast in winter. The bright yellow flowers are borne in erect sprays up to 8" long. Berries are of the usual “mahonia blue”. This is definitely one for shady nooks, performing better near the coast and in the mountains than in areas with hot, dry summers. Otherwise it is trouble-free.
nevinii. My favorite among several large, bushy dryland species. It can grow as much as 15’ tall but usually remains in the 6-10’ range, and is at least as broad as tall. Younger stems are closely lined by 2-3" bluish to greyish green leaves, tinged with pink in new growth. Each leaf is divided into 3-5 toothed, pointed leaflets. The berries are orange to scarlet and quite decorative. One of the most drought tolerant mahonias. Evidently hardy to 10oF. or less.
pinnata ‘Ken Hartman’. California holly grape. This is the best-known selection of our common native, though not as ornamental as ‘Skylark’, below. It grows at least 6’ high, with considerably greater potential spread in time. Individual trunks are upright, their short side branches crowded with spiny, wavy-edged leaves, bronze in new growth and dark green when mature. They have the polished surface typical of this species. Generous sprays of flower clusters are borne at the shoot tips in summer, giving way to typical dark blue berries in fall. A useful specimen shrub and tall hedge. 10oF. or below.
repens. A mountain dweller, ranging widely over the western U.S. It is creeping in habit, producing erect shoots usually 1-2’ tall at intervals along the rhizomes. The leaves are relatively short, with broad leaflets of dark bluish green. In winter they are brilliantly plum-colored. Flowers and berries are carried in short clusters. Below 0oF.
sikkimensis. This is a rare and wonderful mahonia, recently received from the Strybing Arboretum. It grows at a moderate pace to perhaps 8-10’, slowly branching and filling in. It has attractive pale bark. The leaves suggest the more familiar M. lomariifolia but are much showier. They measure up to 2’ long and have several pairs of large leaflets. These show beautiful networks of indented, lighter veins and have strongly crisped, spiny margins. They are bronze to plum purple in new growth, later deep green and shiny above, pale beneath. The flower sprays are long and many, like those of M. lomariifolia, and carry large bright yellow flowers. Hardy to 20oF. or less–possibly much less. Like M. nervosa, above, this is a plant for mild-summer climates and shady nooks.
‘Skylark’. My own selection from a seedling crop, this may be either M. pinnata, the California holly grape, or a chance bee hybrid between it and M. aquifolium. It is a roundish, closely branched shrub of 5’ or more. Its 6" leaves are dark green with a highly polished surface, brilliant red in new growth and purple-tinted in winter. The leaflets are broader and less crinkled than those of typical M. pinnata, but nearly as spiny. The spring flowers and summer berries are borne in densely clustered 4-6" spikes. 10oF. or below.