Thunbergia grandiflora aka Bengal Clockvine

Thunbergia grandiflora is a vine that stays green year-round. It belongs to the Acanthaceae family. People call it blue trumpet vine or Bengal clock vine. Its native range spans central Nepal and southern China. It also includes Peninsular Malaysia. It grows in wet tropical regions and in thickets. Garden plants reach about 13–26 feet (4–8 m) tall. Their spread reaches about 5–8 feet (1.5–2.5 m). Stems can reach 33 feet (10 m) or more.

This vine grows fast and lives for more than one year. Its woody stems wind around supports as they grow. It can also trail over the ground and nearby plants. Its heart-shaped leaves have large teeth along their edges. The leaves stay green all year. Flowers shaped like trumpets hang in groups called racemes. Each flower spans about 2.8 inches (7 cm). The blooms are pale violet-blue, with yellow inside the throat. Some plants bear white flowers instead of violet ones. In tropical climates, the vine can bloom all year.

Outdoors, it grows best in full sun or part shade. It prefers rich, moist soil that drains well. RHS lists loam as a soil choice. It also accepts acid, neutral, or alkaline soil. Under glass, give it bright light screened from hot sun. Use a peat-free potting mix based on loam. Give it a moderate amount of water during growth. Water less when growth slows. RHS advises a general liquid feed each month during growth. RHS rates it H1B, for summer outdoor use in Britain. Chicago Botanic Garden lists USDA zones 8–11.

The vine covers trellises, arbors, fences, and other garden supports. In colder places, gardeners grow it as an annual. It also suits pots, hanging baskets, and growing indoors. Its flowers draw butterflies, and the plant draws birds. Give the vine room to grow to its full form. Cutting it back hard to limit size can reduce blooms. Plants can take five to ten years to reach maturity. Grow new plants from seed or softwood cuttings.

Serious diseases are not a usual problem. Under glass, watch for whiteflies and spider mites. Also watch for aphids and scale. Escaped plants can invade native habitats and smother other plants. Useful Tropical Plants records cooked leaves as a local vegetable. It also reports a traditional use of leaves for snake bites. That use does not prove that the leaves work as medicine. The same source lists no known hazards. This does not confirm safety for people or pets.