Cape plumbago

Sun

Full sun for the best flowering; tolerates partial shade but becomes looser and flowers less.

Water

Water regularly while establishing. Established plants tolerate some drought, but flower better with deep watering during prolonged dry weather; avoid persistently wet roots.

Soil

Well-drained soil, including sandy or loamy soil. Tolerates a range of pH levels, though strongly alkaline conditions can cause yellow leaves.

Height

6-10 ft (1.8-3 m), potentially taller when trained against a wall

Spread

6-10 ft (1.8-3 m)

Flowers

Pale sky-blue flowers from late spring into autumn; flowering can continue for much of the year in frost-free climates. White-flowered forms are also available.

Foliage

Evergreen. Soft green, oblong leaves on slender, arching stems; small ear-like lobes occur at the leaf bases.

Growth

Fast in warm conditions.

Care needed

Medium

• Pollinators
• Drought tolerant
• Heat tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Hard

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   4 ft (1.1 m)

3. After 2 years

   5 ft (1.7 m)

4. After 3 years

   7 ft (2.3 m)

5. After 5 years

   8 ft (2.4 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Invasive in

Australia

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Water new plants deeply whenever the root zone begins to dry; reduce watering once established.
• Grow container plants in pots with drainage holes and let the compost surface dry slightly between waterings.
• Apply a balanced fertiliser in spring; avoid heavy nitrogen feeding, which encourages leafy growth at the expense of flowers.
• Mulch the root area, keeping mulch clear of the main stems.
• Tie long stems to wires or a trellis if you want wall coverage; they will not attach themselves.
• Move containers under cover before frost, keeping them bright, cool and only lightly watered through winter.

Pruning. In late winter or early spring, after the risk of damaging frost has passed, remove dead stems and shorten vigorous growth to maintain the required size. Lightly trim wayward shoots after a flush of flowers; repeated shearing removes developing flower buds.

Late winter

Check overwintering container plants for whitefly and spider mites; keep watering restrained.

Early spring

Prune established plants once damaging frosts are unlikely, then apply a balanced fertiliser.

Late spring

Plant out or move pots outdoors after frost risk has passed, gradually introducing sheltered plants to direct sun.

Summer

Water during dry spells and tie new stems into supports before they become tangled.

Late summer

Take semi-ripe cuttings from healthy, non-flowering shoots.

Autumn

In cold climates, bring pots into bright, frost-free shelter before the first frost; reduce feeding and watering.

• Train against a sunny wall or fence for a loose covering of blue flowers.
• Use as an informal flowering hedge where there is room for arching stems.
• Let it spill over a retaining wall, keeping growth clear of paths.
• Grow in a large terrace container with white pelargoniums or silver-leaved plants.
• Combine with lavender and salvias in a sunny, well-drained border for a long blue-and-purple flowering season.

Garden styles it suits: Mediterranean, Coastal, Cottage garden, Modern tropical, Blues and silvers and Pastel border.

Plant it with: Lavender, Rosemary, Agapanthus, Salvias, Pelargoniums and Society garlic.

Wildlife: Flowers provide nectar for butterflies and other visiting insects. The sticky flower calyces can catch small insects and cling to clothing or animal fur.

• Whitefly, especially under glass: inspect leaf undersides, use insecticidal soap labelled for the pest, and repeat as directed.
• Spider mites in hot, dry sheltered conditions: look for fine webbing and stippled leaves; rinse foliage and use a labelled mite treatment if needed.
• Yellow leaves with green veins in alkaline soil: check drainage and soil pH; apply chelated iron suitable for alkaline conditions if iron deficiency is confirmed.
• Poor flowering: provide more direct sun, reduce nitrogen feeding and avoid frequent clipping of shoot tips.

Contains irritating compounds, including plumbagin, particularly in the roots; leaves and stems should also be treated as potentially harmful. Sap can cause skin irritation, and chewing or swallowing plant material can cause mouth irritation and digestive upset in people and pets, including cats and dogs. Horse-specific toxicity information is limited, so do not allow grazing. Wear gloves when pruning and seek medical or veterinary advice after ingestion.

Where it spreads. Can spread by suckers and escape gardens in warm climates. It is regarded as an environmental weed in parts of Queensland and New South Wales, Australia, and is naturalized in Hawaii. Check local guidance before planting near bushland or other natural areas.

• Hardy blue plumbago (Ceratostigma plumbaginoides)

  A low, spreading herbaceous perennial rather than a tall, sprawling shrub; it has deeper blue flowers, reddish calyces and leaves that turn red in autumn.

• Chinese plumbago (Ceratostigma willmottianum)

  A smaller deciduous shrub with vivid blue flowers, reddish stems and strong autumn leaf colour; Cape plumbago has paler, long-tubed flowers and remains evergreen in frost-free conditions.

Cape refers to its South African origin, while auriculata means 'eared', describing the small ear-like lobes at the leaf bases.

Propagation. Take softwood cuttings in spring or semi-ripe cuttings in late summer and root them in a free-draining propagation mix with gentle warmth. Rooted suckers can also be separated from established plants.

Accepted botanical name

Plumbago auriculata

In the US and Canada

Introduced in Hawaii, the lower 48 states, Puerto Rico and US Virgin Islands.

Native range

Cape Provinces, Free State, KwaZulu-Natal, Mozambique and Northern Provinces.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.