Japanese mahonia

Japanese mahonia: how do you recognise it?

Habit

Broad, rather open shrub about 2 m high and wide, with thick, upright stems.

Leaves

Pinnate, 30–45 cm long, with 7–19 stiff, glossy dark green leaflets with spiny teeth. In cold, sunny winters they sometimes turn red.

Flowers

Long, spreading or drooping sprays of 10–20 cm made up of small pale yellow bells, from November to March.

Scent

Sweet and strong, similar to lily of the valley; on a mild day you can smell it from several metres away.

Fruit

Blue-black berries with a blue-grey bloom, in spring.

Flowering: November–March · Plants: April–May and September–October · Pruning: April

Why grow it?

• Flowers from November to March, with a lovely scent in the winter garden.
• An important food source for bumblebees and bees on mild winter days.
• The blue-black berries in spring are popular with blackbirds and other birds.
• Thrives in partial and full shade, under trees or on the north side of the house.
• The large, spiny leaves give strong, almost exotic structure all year.
• Low maintenance: one prune after flowering is enough.

Japanese mahonia: where does it grow best?

• Partial to full shade; in full sun the leaves may discolour and scorch.
• Humus-rich soil: sand, loam or clay, acid to chalky, preferably not too dry.
• Moderately moist; under trees, give extra water and mulch in dry spells.
• Sheltered from cold, drying winds, which damage the leaves and flower sprays.
• Allow 1.5–2 m per plant.

Light

Partial shade and shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal

Size

2 m tall, 2 m wide

Hardiness

Hardy (to -18 °C)

Goes well with

• Hellebore: Flowers in the same months, in shade at the foot of the shrub.
• Barrenwort: A graceful ground cover for dry shade under shrubs.
• Ferns: Soft green fronds beside the stiff, spiny leaves.
• Snowdrop: White bells beneath the yellow sprays in February.
• Red-barked dogwood: Red winter stems that contrast beautifully with the yellow flowers.

Japanese mahonia: when and how to plant it?

Plant in April–May and September–October.

1. Plant in April–May or September–October, when the soil is neither frozen nor waterlogged.
2. Dig a hole twice as wide as the root ball and mix in a few spadefuls of compost or leaf mould.
3. Set the plant at the same depth as in the pot and firm the soil well.
4. Water thoroughly straight away, even if it is raining.
5. Spread a mulch of leaf mould or bark around the base.

Care

Water

Regularly in dry weather during the first year. After that only in long dry spells, especially under trees.

Feeding

Some compost or organic shrub fertiliser in April.

Mulching

A layer of leaf mould or bark in spring keeps the soil cool and moist.

Old leaves

Fallen brown leaves can be left as mulch; wear gloves if you clear them up.

Gloves

The leaves are very prickly: always wear sturdy gloves.

Tip: Plant it by a path or front door you pass every day in winter, but not right beside it: you enjoy the scent without getting pricked by the leaves.

Japanese mahonia: when to prune it?

Pruning months: April.

When: After flowering, in April. It needs little pruning.

How:

• Cut overlong, bare stems back to just above a rosette of leaves or a few buds lower down; they will reshoot there.
• Renovate an old, leggy shrub over two to three years: each year cut a third of the oldest stems back low.
• Remove dead and damaged stems at the base.
• Leave the faded sprays in place if you want berries for the birds.

Caution: Do not prune in summer or autumn: you would remove the flower buds for the coming winter.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Leaf-bud cuttings

In October–November: a piece of stem with one leaf and a bud, the leaf shortened, in moist cutting compost in a cold frame or greenhouse. Rooting takes a few months.

Seed

In late spring, take the seeds from ripe berries and sow them straight away in a tray outdoors. They often germinate only after a winter.

Japanese mahonia: how does it get through the winter?

Hardy to −18 °C: protect young plants.

• Hardy to about −18 °C: no protection is needed in Belgium.
• Hard frost and cold wind can brown the flowers and leaves; the shrub simply reshoots in spring.
• In a large pot: stand it against a wall and wrap the pot in hessian so the roots do not freeze.

Diseases and pests

• Rust: Orange-brown pustules under the leaves, purplish-brown spots on top. Remove affected leaves and keep growth airy.
• Powdery mildew: A white coating on the leaves, especially in dry weather. Water, remove affected leaves and allow space.
• Red or scorched leaves: Caused by strong sun or cold, drying wind. Choose a more sheltered, shadier spot; new leaves appear in spring.
• Long, bare stems: Older shrubs become bare at the base. Prune back gradually after flowering to rejuvenate.

Through the year

• January: In flower. Bumblebees on mild days.
• February: Scented flowers.
• March: End of flowering.
• April: Prune after flowering. Add compost and mulch. Plant.
• May: Blue-black berries for the birds. Plant.
• June: Sow seed from the berries. Water in dry weather.
• September: Plant.
• October: Plant. Take leaf-bud cuttings.
• November: Flowering begins.
• December: Scented flowers in the winter garden.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Birds

Berries, seeds or insects as food, or a place to nest.

Did you know?

• The name Mahonia honours Bernard McMahon, a gardener and nurseryman in Philadelphia around 1800.
• Well-known cultivars such as ‘Charity’ and ‘Winter Sun’ belong to Mahonia × media, a cross between this species and Mahonia lomariifolia.
• Recent botanical research places the mahonias in the genus Berberis, which is why it is now also called Berberis japonica.