Chinese plumbago

Chinese plumbago: how do you recognise it?

Habit

Loose, rounded shrub 60–100 cm tall and about as wide, with thin, reddish stems.

Leaves

Diamond-shaped to obovate, with bristly hairs along the edge; green, turning red in autumn.

Flowers

Five-lobed flowers about 2 cm across in clusters at the stem tips, from August to October.

Colour

Bright sky blue to cobalt blue, with reddish calyces.

Roots

Fine and branching; they cannot cope with soil that stays wet in winter.

Flowering: August–October · Plants: April–May · Pruning: April

Why grow it?

• Sky-blue flowers from August to October, when the garden can use a fresh colour.
• Red autumn colour while it is still in flower: blue and red on the same shrub.
• Bees and butterflies visit the flowers.
• Drought-tolerant and happy in poor, free-draining soil.
• Small and easy: one prune a year is enough.

Chinese plumbago: where does it grow best?

• Full sun, for the most flowers and the best autumn colour.
• Free-draining sandy or loamy soil, acid to chalky. On heavy clay it stays too wet.
• Dry to moist soil: it tolerates drought far better than waterlogging.
• A warm spot against a wall, in a gravel garden or a rock garden is ideal.
• Allow 60–80 cm between plants.

Light

Sun

Soil type

Sand or loam

Acidity

Not fussy

Moisture

Dry or normal

Size

1 m tall, 1 m wide

Hardiness

Hardy (to -15 °C)

Goes well with

• Ice plant: Pink flower heads at the same time, also loved by bees and butterflies.
• Gaura: Airy white flowers in the same sunny, dry spot, well into autumn.
• Lavender: Silver-grey foliage and earlier flowers, for blue all summer long.
• Ornamental grasses: Plumes that turn golden in autumn beside the red leaves and blue flowers.

Chinese plumbago: when and how to plant it?

Plant in April–May.

1. Plant in April or May, so it is well rooted before winter.
2. Dig a hole twice as wide as the pot and loosen the bottom. On loamy soil, mix in some coarse sand or gravel.
3. Set the plant at the same depth as it was in the pot and firm the soil well.
4. Space plants 60–80 cm apart.
5. Water in thoroughly straight away, and again in dry spells during the first weeks.
6. Mulch with gravel or a thin layer of compost.

Care

Watering

In the first year, weekly in dry weather. After that rarely needed, except in pots.

Feeding

A handful of compost in April. More feed is not needed and mainly produces leaves.

Mulching

A thin layer of gravel or compost keeps weeds down and the base dry.

Patience in spring

It is late to leaf out, often not until May. Do not dig it up thinking it has died.

Deadheading

Not needed. Leave the stems standing until the April prune.

Tip: It leafs out late, often not until May, so do not be too quick to dig it up thinking it has died. Plant it at the front of the border so you can enjoy the late flowers and autumn colour.

Chinese plumbago: when to prune it?

Pruning months: April.

When: In April, once the hardest frosts are over and before the new shoots appear.

How:

• Cut all stems back to just above the ground.
• Remove dead and frost-damaged wood.
• Leave the old stems over winter: they protect the base from frost.
• Not sure whether a stem is alive? Wait until May and you will see where it reshoots.

Caution: It flowers on new wood: a hard prune in April costs no flowers, but pruning in summer or autumn does.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Softwood cuttings

In May–June: cuttings of about 8 cm from young shoots, lower leaves removed, in moist cutting compost under plastic.

Semi-ripe cuttings

In July–August in the same way. Keep them frost-free over their first winter.

Layering

In summer, peg a low stem to the ground and cover it with a little soil. Sever and replant it after a year.

Chinese plumbago: how does it get through the winter?

Hardy to −15 °C: protect young plants.

• Hardy to about −15 °C. In a severe winter it often dies back to the ground, but usually reshoots in May.
• Leave the stems over winter for protection. In a cold, exposed garden you can cover the base with a layer of leaves.
• Wet soil in winter is a bigger threat than frost: make sure drainage is good.
• In a pot: stand it against a sheltered wall and wrap the pot in hessian.

Diseases and pests

• Root rot: The plant struggles and dies on heavy, wet soil. Move it to a sunny, free-draining spot.
• Late leafing: Not a disease: it is simply late. Scratch a stem with your nail; if it is green underneath, it is alive.
• Powdery mildew: White powder on the leaves in a dry late summer. Water at the base, give it space and remove affected leaves.
• Frost damage: Dead stems after a hard winter. Cut them out in April; new shoots come from the base.

Through the year

• March: Do not prune yet. Weed around the base.
• April: Cut back to just above the ground. Plant. Give a handful of compost.
• May: Plant. New shoots appear, sometimes late in the month. Take softwood cuttings.
• June: Water young plants in dry weather.
• July: Water in long dry spells. Take semi-ripe cuttings.
• August: Flowering begins.
• September: Full flower. The leaves start to turn red.
• October: Last flowers and red autumn colour.
• November: Leave the stems standing. Move pots to shelter.
• December: Dormant.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• It is named after Ellen Willmott, an English gardener who was among the first to raise it from seed collected in China by Ernest Wilson.
• It belongs to the plumbago family, like the conservatory Plumbago and the sea thrift of the coast.
• The name Ceratostigma comes from Greek and refers to the horn-shaped stigma of the flower.