Thunbergia

Thunbergia flowers

A vigorous, twining tender climber. Suitable for warm sheltered gardens. Usually grown as an annual in the UK. The prolific showy flowers stand out well against its rich green leaves in summer.

Family: Acanthaceae
Botanical Name: Thunbergia
Common Names: Black-eyed Susan, bright eyes, clock vine.

Foliage: Evergreen, heart-shaped or oval toothed leaves.

Flowers: Five petal open trumpet-shaped flowers. Usually orange/yellow with a dark centre. Often followed by pea-sized winged seed capsules.

Flowering Period: June to September.

Soil: Moist but well-drained soil (chalk, clay or loam). Acid, alkaline or neutral pH.

Conditions: Full sun. Plant in a west or south facing aspect, in a sheltered location.

Habit: Spreading, climbing, self-clinging.

Type: Half-hardy Annual.

Origin: Africa and Asia.

Hardiness: Tender in UK, protect from frost.

Planting and Growing Thunbergia

Easy-to-grow and low-maintenance with a long flowering season. Thunbergia is good conservatory perennial, which is less demanding that other tender plants.

Can also be grown as an annual outside, against a warm sheltered sunny wall, fence or pergola. Plant in a humus rich, fertile, well-drained soil.

Provide support wires, canes or netting for the stems to twine round. Black-eyed Susan can quickly cover a small area within a single growing season. They will also trail, making them ideal for large baskets and containers.

Taking Care of Thunbergia

Water well during dry spells. Feed every few weeks with a liquid fertilizer for flowering plants.

Pruning Thunbergia

Not necessary. Pinch off the growing tips to control height and spread. Pull up and discard annuals to the compost heap once flowering has finished.

Pests and Diseases

Susceptible to attack by Aphids and other glasshouse pests if grown under glass. Can be affected by powdery mildews.

Propagating Thunbergia

Sow in early spring under glass, in individual pots of seed compost. Harden off before planting out at the end of May. Alternatively, sow in a well prepared seed bed, where they are to flower, around late April-May.

Popular Varieties of Thunbergia

Thunbergia alata (black-eyed susan) is a twining plant with heart shaped, mid green leaves and striking orange-yellow flowers, with a dark brown or purple centre. Height up to 10ft (3m), spread 1.5ft (45cm). Cultivars include:

  • 'African Sunset' has peachy-pink flowers with dark centre. Available from Sarah Raven.
  • 'Arizona Dark Red' bears a mass of richly coloured summer flowers. For sale at Crocus.
  • 'Arizona Rose Sensation' magenta-pink. Available from You Garden.
  • 'Arizona Pink Beauty' rose-pink.
  • 'Arizona White Halo' ebony-white.
  • 'Blushing Susie' predominantly red flowers, with shades of ivory and apricot adding contrast. Climbing to 36-60in (90-150cm). For sale at Thompson & Morgan.
  • 'Sunny Suzy Brownie' produces a profusion of chocolate-red to burnt orange flowers. For sale at Crocus.
  • 'Superstar Orange' large bright orange flowers. For sale at Thompson & Morgan.
  • 'Suzie Orange with Eye' (Suzie Series) incredibly generous with its blooms. For sale at Crocus.
  • 'Suzie White Black Eye' (Suzie Series) great for adding long-lasting summer colour. For sale at Crocus.

Thunbergia fragrans 'Angels Wings' yellow flowers with a white eye.