Japanese hydrangea vine

Japanese hydrangea vine: how do you recognise it?

Habit

Deciduous climber that clings with aerial roots; after many years 8–12 m tall and 3–4 m wide.

Leaf

Broadly oval to heart-shaped, 10–15 cm, coarsely toothed, on long stalks; dark green, yellow in autumn.

Flower

Flat heads up to 25 cm across in July: small cream-white fertile flowers with loose white bracts around the edge.

Bracts

Each sterile flower has a single large oval bract of 3–4 cm on a long stalk.

Roots

Aerial roots along the stems; in the soil, a shallow, branching root system that needs moisture.

Flowering: July · Plants: March–April and October · Pruning: August

Why grow it?

• One of the few climbers that flowers freely in shade, even on a north-facing wall.
• Self-clinging: no wires or trellis needed.
• Large, elegant white flower heads in July that attract bees.
• Fully hardy and rarely troubled by disease.
• Yellow autumn colour and faded flower heads that stay attractive into autumn.

Japanese hydrangea vine: where does it grow best?

• Partial or full shade: a north- or east-facing wall, a fence or a large tree trunk.
• Loose, humus-rich soil: sand or loam, acid to neutral.
• Moisture-retentive to moist; do not let it dry out, especially in the first years.
• No full midday sun, which scorches the leaves.
• Plant 30 cm from the wall and allow 3–4 m of width.

Light

Partial shade and shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal or wet

Size

10 m tall, 4 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Ferns: Fresh green underplanting in the same shade.
• Hosta: Large leaves at the foot of the shady wall.
• Climbing hydrangea: Flowers in June; the Japanese hydrangea vine takes over in July.
• Lenten rose: Flowers at the base in spring, while the climber is still bare.
• Barrenwort: Ground cover that tolerates shade and dry spots at the foot of a wall.

Japanese hydrangea vine: when and how to plant it?

Plant in March–April and October.

1. Plant in March–April or October, when the soil is neither frozen nor waterlogged.
2. Dig a hole twice as wide as the root ball and mix in plenty of compost or leaf mould.
3. Set the plant at the same depth as in its pot, 30 cm from the wall, and lean the stems against the wall.
4. Tie the first shoots to the wall with a cane or wire until the aerial roots take hold.
5. Water in well and spread a thick layer of leaf mould around the base.

Care

Water

Regularly in dry spells for the first two years; little rain falls at the foot of a wall.

Feeding

Compost or leaf mould around the base in April.

Mulching

A layer of leaf mould every spring keeps the soil cool, moist and rich in humus.

Support

Only at first: tie in young shoots until they cling by themselves.

Patience

For the first two or three years it grows slowly and flowers little; after that it speeds up.

Tip: Tie the first shoots to the wall and give leaf mould every spring: after two or three slow years it clings and grows away freely.

Japanese hydrangea vine: when to prune it?

Pruning months: August.

When: Little pruning needed. After flowering, in August, cut back anything too long or sticking out too far.

How:

• Cut shoots growing away from the wall back to two or three buds above the permanent framework.
• Keep windows, gutters and roof tiles clear by removing the tips that reach them.
• Remove dead and damaged branches.
• You can leave the faded flower heads; they still look good in autumn.

Caution: Do not prune hard: it flowers on short side shoots, and a hard prune costs a few years of flowering.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Semi-ripe cuttings

In July–August, take 10–15 cm cuttings and root them in moist cutting compost under plastic, in shade. They are slow to root.

Layering

In spring, peg a low, flexible stem into the soil; sever and replant it after a year.

Japanese hydrangea vine: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy, to about −25 °C: no protection needed in Belgium.
• Give young plants a thick layer of leaf mould around the base in autumn.
• The leaves drop in autumn; the stems stay firmly attached to the wall.

Diseases and pests

• Slow start: Little growth and no flowers in the first years. That is normal: give compost, water and patience.
• Brown leaf edges: Too much sun or drought. Water, mulch the base and make sure it gets afternoon shade.
• Stems coming away: Young stems do not cling yet. Tie them in until the aerial roots take hold.
• Aphids: On young shoots in May. Hose them off; ladybirds help.

Through the year

• March: Planting. Compost or leaf mould around the base.
• April: Planting. Tie young shoots to the wall.
• May: Water in dry spells. Watch for aphids.
• June: Flower buds appear. Water in dry spells.
• July: Flowering. Take cuttings.
• August: Prune after flowering: shorten shoots that stick out.
• October: Planting. Yellow autumn colour. Mulch.
• November: Leaf fall. Dormant.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• In the climbing hydrangea each sterile flower has four bracts, in this plant only one. That makes them easy to tell apart.
• The name comes from the Greek schizo (to split) and phragma (wall), after the fruits that split open between their ribs.
• The aerial roots grip firmly: if you ever remove the plant, marks will remain on the wall.