Synonyms

Mahonia pinnata 'Pinnacle' and Mahonia aquifolium 'Fascicularis'

Family

Berberidaceae

Common name/s ?

Oregon grape 'Pinnacle'.

Skill rating

Easy

Origin

North/Central America

Type of plant ?

Evergreen, perennial shrub.

Hardiness zone ?

RHS zone

Hardy

EGF zone

H4

USDA zone

5-8

Eventual size

To 1.5m height by 2m width.

Growth rate ?

Slow; it will reach its full height in 10 to 20 years.

Shape it grows into

Upright, spreading shrub.

Season/s of interest

Flowers in spring and berries in summer/autumn. Evergreen leaves throughout the year.

Where to grow it

Happy in part or full shade.
Prefers well drained to moist soil.

Will grow in any soil type (in terms of texture and pH). Can be grown in exposed or sheltered sites.

Mahonia x wagneri 'Pinnacle'

Features

The evergreen, spiky, glossy leaves (on attractively red stems) are bronzed when young, becoming dark green with age. Clusters of yellow flowers appear in spring followed by purple/black berries in summer and autumn. The stamen of the flowers spring inwards when touched. The woody stems are deeply fissured on the outside and yellow on the inside.

What to use it for

Good in beds and borders and would be particularly suited to a woodland setting. It can be used as tall ground cover and on banks or slopes. The berries make it a useful addition to wildlife gardens.

As it requires little looking after and is drought resistant, it is good for a low maintenance garden.

How to look after it

Requires very little care as it is hardy and drought tolerant. Pruning is only needed to keep it neat (see below).

How to prune it

Prune in spring, once it has flowered. Remove any unwanted suckers around the edge of the plant to control its spread. If you want to keep it dense to have good ground cover, then you can shear it to just above ground level every other year (or annually), otherwise little pruning is required.

Neglected shrubs can be renovated by cutting old branches down to ground level, leaving younger stems intact.

How to propagate it

Semi-ripe cuttings can be taken from midsummer to autumn; take leaf-bud cuttings with two or more nodes (the nodes on mahonia plants are quite close together), make a wound on one side of the stem about 1cm long and reduce the leaf to 2 or 3 pairs of leaflets. Put them in cutting compost and apply bottom heat of around 15 to 20°C. Alternatively, take hardwood cuttings in winter. Plants will flower from cuttings in three years.

Seeds can be collected from the berries when they are ripe (from early summer). Clean them thoroughly before sowing them. Mahonias often cross-pollinate, so while the resulting plants make not come true to type, you might get something you like anyway! Cultivars are unlikely to come true from seed.

Common problems

Generally this plant is not attacked by pests, however mahonia rust, berberis rusts and powdery mildews may be a problem.

Other useful information

This plant has received the RHS Award of Garden Merit.

Native Americans used the roots of many Mahonia species for medicinal purposes.

This plant is a hybrid between M. aquifolia and M. pinnata.

The genus Mahonia was so named in 1818 to commemorate the late Bernard McMahon, an Irish-born nurseryman who settled in Philadelphia in the late 1700s.