Plant 115

Thunbergia mysorensis T.Anderson (Acanthaceae)


Indian clock vine

Thunbergia mysorensis is a stunning, vigorous vine from southern India where it climbs through trees in tropical montane forests. It has become naturalised in Mediterranean climates and elsewhere due to its popularity as an ornamental plant.

The generic name commemorates the Swedish botanist Carl Peter Thunberg, one of Carl Linnaeus's pupils and a prolific collector of Asian plants. The species epithet is a reference to the city of Mysore (today Mysuru) in the Indian state of Karnataka.

Thunbergia mysorensis has pendulous racemes of striking, red and yellow inflorescences. Each flower is up to five centimetres long with showy red bracts. The tubular flowers are bilaterally symmetrical, consisting of five fused petals. The petal tips are coloured red which are reflexed to expose the yellow throat, the large stamens and feathered stigmas.

In its native range, Thunbergia mysorensis is pollinated by sunbirds. Where it has naturalised in the Americas its abundant nectar is a source of food for hummingbirds. As they feed, the heads of visiting birds become dusted in pollen, which is transferred to other flowers. Pollination is completed because of the position of the anthers and the stigmas, held against the inner and upper surface of the reflexed corolla.

Most of the approximately 250 genera and 3,000 species in the Acanthaceae originate from tropical and sub-tropical regions. They are usually herbs, shrubs and climbers, but some are Australian and Central American mangroves species. Many Acanthaceae fruits are dehiscent capsules within which seeds are held on hook-like structures called retinacula. The genus Thunbergia is however an exception. Acanthaceae leaves have enlarged cells called cystoliths, containing calcium carbonate crystals. Acanthaceae also show enormous variation in the size, shape and structure of their pollen, which may be useful for identification of some genera.

In temperate zones, Thunbergia mysorensis is a conservatory or greenhouse plant. It requires a winter minimum of 12 degrees celsius in full-sun or partial shade. The stems twine clock-wise and as they mature this produces an ornamental effect, similar to Wisteria floribunda. Pruning is best completed in spring by thinning the crowded stems. It will produce single flowers in the axils of the leaves, but to produce its striking pendulous racemes, this climber requires a run of several metres. These inflorescences are often more than 30 cm in length and create a dramatic display. Thunbergia mysorensis originates from a monsoon climate and so requires plenty of water over summer.

Further reading

Huxley A. 1992. Dictionary of gardening. The Royal Horticultural Society.

Kate Pritchard