Cape Leadwort - Plumbago: Growing and Care

Botany and description

The botanical genus Plumbago belongs to the Plumbaginaceae family, a group of plants known for their members adapted to a variety of habitats, often in saline or calcareous environments. The genus name “Plumbago” is said to derive from the Latin word for lead (“plumbum”), due to an ancient belief that these plants could cure lead poisoning or wounds caused by lead projectiles. The genus comprises about twenty species, including:

• Plumbago auriculata (formerly Plumbago capensis): Cape Leadwort or Cape Plumbago
• Plumbago europaea: European Leadwort
• Plumbago indica: Scarlet Leadwort or Indian Leadwort
• Plumbago zeylanica: Ceylon Leadwort

Plumbago auriculata, Plumbao europaea, Plumbago indica (© Teresa Grau Ros) and Plumbago zeylanica.

The Plumbago auriculata, often referred to as Cape Leadwort, is undoubtedly the most widespread and cultivated species within the genus. Characterised by bright blue flowers, sometimes pale blue or white, this climbing or shrubby plant is native to South Africa. It is prized for its abundant and prolonged flowering, which can last from summer to autumn, or even all year round in warmer climates.

Plumbago capensis, botanical plate.

Cape Leadwort has a semi-erect to creeping habit, making it extremely versatile in the garden. This plant can reach a height of 1 to 2 metres and spread to a similar width, offering a bushy and spreading growth. Thanks to its long, flexible stems, Plumbago auriculata can be easily trained to climb supports or trellises, making it an excellent choice for pergolas, walls or fences. But Plumbago auriculata is also used as ground cover in large areas where its dense foliage can quickly cover the ground, preventing weed growth and helping to control soil erosion.

The evergreen leaves of Plumbago auriculata are green, oblong to ovate, measuring about 5 cm long. They provide a dense, lush backdrop against which the sky blue to pale blue flowers (sometimes white depending on the variety, for example Plumbago auriculata ‘Alba’) stand out particularly well. These flowers, clustered in terminal cyme-shaped inflorescences, bloom abundantly from summer to autumn, and in warm climates, they may even continue to flower throughout the year. Each flower is tubular, opening into five spreading lobes that form an almost flat corolla. This shape is adapted to attract and facilitate access for pollinators such as butterflies. The flowers measure about 2 to 3 cm in diameter.

The flowers are grouped in terminal inflorescences, taking the form of feathery cymes. These clusters can be quite dense, with each inflorescence bearing numerous flowers that together create a spectacular visual effect. The inflorescences can measure up to 15 cm long, contributing to the plant’s bushy, spreading appearance. At the centre of each flower are five prominent stamens encircling the style, adding to the flower’s decorative appeal. Plumbago auriculata is adapted for cross-pollination, with pollinators playing a key role in the fertilisation process.

Flowers with more or less intense blue colour depending on exposure and time of day

After pollination, the plant produces a small fruit which is a capsule containing the seeds. However, in gardens, the main interest lies in the flowering rather than the fruiting.

The best varieties

Plumbago auriculata

Plumbago auriculata, or Cape Leadwort, is an exuberant semi-climbing bush, highly favoured by gardeners in our temperate regions where frost is neither too severe nor too prolonged. This plant native to South Africa indeed loves the sun and requires warmth to provide its endless flowering, which makes it disappear for long months under a cloud of light, pure celestial blue.

• Flowering time August to November
• Height at maturity 1,50 m

See the product sheet

Plumbago auriculata Dark Blue

Plumbago auriculata Dark Blue, or Cape Leadwort, is an exuberant semi-climbing bush, highly favoured by gardeners in our temperate regions where frost is neither too severe nor too prolonged. This plant native to South Africa indeed loves the sun and requires warmth to provide its endless flowering, which makes it disappear for long months under a cloud of deep blue.

• Flowering time August to November
• Height at maturity 1,50 m

See the product sheet

How to plant a Cape Plumbago?

When to plant?

The ideal time to plant Plumbago auriculata is in spring, after the last frosts, or in autumn in regions with a mild climate. This allows the plant to establish itself and acclimatise before periods of extreme heat or cold.

Where to plant?

Cape Leadwort thrives in full sun or partial shade. Choose a location that receives at least 6 hours of direct sunlight per day to encourage abundant flowering. The plant also prefers a neutral to slightly acidic, well-drained, fertile soil rich in organic matter.

The hardiness of Plumbago auriculata can be classified in USDA zone 9-11, meaning it can tolerate minimum temperatures down to -6.7°C (-9°C theoretically for the ‘Dark Blue’ variety). In these zones, Plumbago auriculata can be grown in the ground as an evergreen perennial, enjoying near-continuous flowering throughout the year in warmer climates. In regions where winter temperatures regularly drop below -6.7°C, it is advisable to grow Plumbago auriculata in pots or containers so it can be moved to a sheltered space during the coldest months. This method protects it from frost and ensures a safe dormancy period for its root system.

How to plant a plumbago?

• Before planting, loosen the soil to a depth of 30 to 40 cm and add compost to improve the soil.
• Dig a planting hole twice as wide as the plant’s pot.
• Gently remove the Plumbago from its pot, place it in the hole, and adjust the height so the base of the plant is level with the ground.
• Fill the hole with the excavated soil, lightly firm it, and water thoroughly to avoid any “air pockets” between the roots and the soil.

Important!: To protect a Plumbago from cold, provide well-drained soil, good mulching at the base, a south-facing wall location, and possibly cover the plant with winter fleece.

A plumbago trained here as a standard

Care for Plumbago

After planting, water the Plumbago auriculata regularly, especially during dry spells, to keep the soil slightly moist. Mulching can help retain soil moisture, reduce weed growth and protect the roots during winter.

Prune the plant lightly after flowering to encourage new growth and more abundant flowering the following year.

Propagation

Propagation by cuttings

Propagation by cuttings is one of the most effective methods to multiply Plumbago auriculata. Choose this technique between April and July, when the plant is in full growth.

• Select healthy, vigorous current-year stems, without flowers, and cut sections about 15 cm long.
• Remove the leaves from the lower third of each cutting to prevent rotting, reduce evapotranspiration and stimulate root formation.
• You may dip the cut end in plant hormone to encourage rooting, though this step is optional.
• Plant the cuttings in a light, well-draining potting mix, such as special cutting compost.
• Keep the substrate moist but not waterlogged, and place the cuttings in a bright spot without direct sunlight.
• Roots should begin developing within a few weeks, after which you can transplant them into individual pots before moving them to the garden.

Division

You can also attempt division on a well-established plant, ideally in spring or autumn.

• Carefully dig up the mother plant, taking care not to damage the roots.
• Gently separate the clump into several sections, each with some roots and healthy shoots.
• Replant the divisions immediately in their new location in the garden or in pots, respecting the plant’s specific soil and exposure requirements.
• Water generously after planting to help the new plants establish.

Pests and Diseases

Plumbago auriculata, like other plumbago species, is generally hardy and not prone to pest attacks or diseases. However, certain conditions can encourage specific problems to arise.

Common Pests

• Aphids: These small sap-sucking insects can weaken the plant and encourage the spread of diseases. To combat them, a treatment based on insecticidal soap or neem oil is effective. Spray the solution on affected areas, ensuring to reach the underside of the leaves where aphids like to hide.
• Red spider mites: These tiny mites prefer hot and dry conditions. They spin fine webs on plants and can cause leaf yellowing. Increasing humidity around the plant can deter them. In case of infestation, applying miticides or neem oil can help control the problem.

Possible Diseases

• Root rot: Caused by excess moisture around the roots, this condition can be fatal for plumbago. Ensure the soil is well-drained and avoid overwatering. If rot is detected, it may be necessary to remove affected parts and replant in fresh, well-drained soil.
• Powdery mildew: This fungus forms a white powdery coating on leaves and stems. It thrives in conditions of high humidity and moderate temperatures. To treat it, reduce humidity around the plant and apply a specific fungicidal treatment according to the manufacturer’s instructions.

Prevention is Key

Prevention is the best strategy to avoid pest and disease problems. Here are some tips:

• Ensure your plumbagos are planted in well-drained soil and in the right location, respecting their sunlight requirements.
• Maintain good air circulation between plants to reduce humidity and the likelihood of fungal infections.
• Regularly inspect your plants for any signs of trouble and act quickly to prevent spread.

How to best pair a Cape leadwort?

Pairing the Plumbago auriculata ‘Dark Blue’ with other plants that share its growing requirements is an excellent way to create harmonious compositions in the garden. Choose companions that thrive under the same sunlight conditions, from full sun to partial shade, and appreciate well-drained soil. The Lavandula x intermedia ‘Dutch Group’, with its blue-violet hues and aromatic foliage, offers a fascinating colour contrast with the deep blue of the Plumbago, while sharing a love for sunny spots and well-drained soil, bringing a Mediterranean touch to the garden. Still within Mediterranean plants, the rosemary ‘Corsican Blue’, with its semi-creeping habit, provides evergreen foliage and blue-mauve flowers that will complement the Plumbago beautifully.

We also appreciate the rosemary-leaved santolina, with its silvery foliage and yellow summer flowers, offering an interesting play of contrasting colours and textures alongside the Plumbago, both enjoying dry conditions. Blue-flowered agapanthus adds vertical interest with their spectacular flowering, sharing similar needs in terms of sunlight exposure and soil quality, ideal for borders or mixed beds. Finally, the lamb’s ear-Stachys byzantina ‘Big Ears’ will create a contrast in colour and texture with its silvery, fuzzy foliage against the green and blue of the Plumbago. All these plants can be grown in pots for a soft, summery ambiance, perfect for a cosy corner to enjoy morning tea in the garden or on a balcony.

Plumbago auriculata, Agapanthus, Stachys byzantina ‘Big Ears’ and Lavandula x intermedia ‘Dutch Group’

Anecdotes

• A curious name!: The genus name “Plumbago” comes from the Latin “plumbum”, meaning lead, due to the ancient belief that the plant could cure lead poisoning. This association with lead also led to its use in traditional remedies for bullet wounds in the Middle Ages, though no scientific evidence supports these medicinal uses.
• Uncertain love!: In the language of flowers, Plumbago symbolises both pure love and uncertain love. This duality likely stems from its ability to thrive with minimal care, representing unconditional love, while having delicate and almost shy flowers, evoking uncertainty.
• Surprisingly tough!: An Plumbago auriculata reportedly survived and flowered after being forgotten in a dark garage for several months, showcasing its remarkable resilience.
• Butterfly restaurant: The Cape Leadwort is not only prized for its beautiful blue or white flowers, but it is also highly attractive to butterflies.
• The name “dentelaire” was assigned to the 18th day of the month of Brumaire in the French Republican calendar or revolutionary calendar, generally corresponding to 8th November in the Gregorian calendar.