Description

General aspect and origins - Thunbergia grandiflora is also known as Bengal trumpet, sky flower or Bengal clock vine. This vine is native to Southeastern Asia, and more precisely to India. It bears wide flowers that are generally sky-blue or lavender-blue. Some varieties (E.g. 'Alba') have pure white flowers.
Leaves - Leaves of the clock vine are opposite, leathery, dark-green and somehow heart-shaped.
Flowers - Thunbergia grandiflora generally has tubular sky-blue flowers, which are 1.5-2.5 in (4-6 cm) wide. These flowers are grouped in terminal clusters.

Culture

This vine can be grown outdoors in frost-free areas. (USDA zones 10b-11) It is sometimes reported to be root-hardy to moderate frosts (24°F-28°F, -2°C to -5°C) but the foliage will be damaged by the slightiest frost.

Some varieties were selected, among which :

T. grandiflora 'Alba' - with pure white flowers

T. grandiflora 'Augusta Blue' - with sky-blue flowers

Note: This vine is considered as an invasive species in some tropical and subtropical areas, including the Hawaii islands (USA), some areas in Australia and Singapore.
Soil - This vine requires a well-drained and fertile ground.

Propagation

This plant can be propagated by seeds in spring, cuttings in late spring to early autumn, and air layers in spring.