Family: Acanthaceae

There are about 100 species of flowering annual or perennial climbers, dwarf plants and shrubs in this genus, mostly occurring in warm regions of central and southern Africa, with some species from Madagascar, India and Asia. With their showy, brightly coloured, funnel-shaped flowers, they make very attractive container or hanging basket plants.

Species

T. alata, black-eyed Susan, is a twining, perennial climber, to 3 m (10 ft) high, from tropical Africa. It has mid-green, triangular or heart-shaped leaves, to about 8 cm (3 in) long, serrated at the margins. From summer through to autumn, it is covered with a profusion of cream to deep orange flowers with purple or brown throats. It is well suited to hanging baskets or pot culture. Cultivar 'Alba' has white flowers with dark throats; 'Aurantiaca' has bright orange flowers with dark throats; and 'Baked' has pure white flowers.

T. erecta, king's mantle or bush clock vine, is an upright or scrambling shrub from tropical Africa, to 2 m (6 ft) high. It has smooth, oval leaves, about 8 cm (3 in) long, and purple flowers, with a deep yellow or white throat. In warm climates, it blooms for much of the year.

T. grandiflora, blue trumpet vine or clock vine, from India, is a climber, to 5 m (16 ft) high, grown for its lovely, drooping clusters of bright blue flowers, with creamy white throats, produced (luring summer and autumn. It has toothed, heartshaped leaves, up to 20 cm (8 in) long.

T. mysorensis, from India, is the most spectacular species. This vigorous climber bears long trusses of flowers, making it a perfect choice for a tall conservatory. The yellow and reddish brown hooded flowers are produced in spring.

Cultivation

All thunbergias are frost-tender. In frost-prone climates, grow them in an intermediate to warm greenhouse or conservatory, in pots of soil-based potting compost. They need good light, but shade from direct, strong sun. Supports will be needed for the climbing stems. Climbers may need pruning in early spring to control size. T. alata is often grown outdoors as a summer annual, in a sheltered, sunny posi­tion with well-drained soil. Outdoors in suitable climates all thunbergias need a sunny spot with well-drained soil. Propagate in spring from seed germinated at 18°C (64°F), from semi-ripe cuttings in summer with basal warmth, or by layering in spring.

Climate

Zone 10 or tropical.