Thunbergia grandiflora (Roxb. ex Rottl.) Roxb.

Global description

Thunbergia grandiflora is a large perennial vine, sub-woody at the base. The leaves are simple, opposite, stalked with widely ovate blade, acute apex, cordate base and margin marked in the lower third by 1 to 2 pairs of pointed lobes. They are scabrous on the upper surface and pubescent on the lower surface. The inflorescence consists of terminal racemes often drooping up to 1 m in length, or with solitary flowers at the axils of leaves. Asymmetric flower, inserted between two leafy bracteoles. Calyx in cushion; corolla light blue, purple to white, in curved tube topped by five rounded lobes,  4 to 7 cm long.

General habit

Climbing and abundantly branched vine, can reach up to several tens of meters long. It can easily cover large trees or vegetation.

Underground system

Tuberous taproot with tendency to produce stoloniferous stem at the surface of the ground, rooting very easily at the nodes.

Stem

The young stem is quadrangular and pubescent, green in color, while the older stem is cylindrical, solid, becoming sub-woody and can measure several centimeters in diameter at the base, for older plants.

Leaves

The leaves are simple, opposite, held by pubescent petiole, 3 to 10 cm long. The leaf blade is broadly oval to triangular, dark green in color, 6 to 22 cm long and 3 to 16 cm wide. Acute to acuminate apex, the base is cordate. The margin is highly variable, can be whole or irregularly serrated, crenate; it is marked at one third of the bottom by 1 to 2 pairs of big pointed lobes. The upper side is scabrous and the underside is pubescent. The leaf blade is marked with 5 to 7 palmate veins at the base.

Inflorescence

Flowers arranged in terminal racemes, measuring up to 1 m long or solitary in the axils of leaves.

Flower

The flower is held by a peduncle, 2 to 10 cm long with, at the base, two small hairy bracts and at the top two large leafy 2 to 4 cm long bracteoles, of oval shape with apiculate top. The bracteoles cover the corolla tube and turn yellow during the blossoming of the flower. The calyx is an annular entire cushion. The corolla is asymmetrical, blue, purple to white, with light yellow tube, 4 to 7 cm long, formed of a bent tube ending in 5 large rounded lobes with sinuated margin, the ventral lobe is slightly longer than the others. 4 equal stamens are inserted into the tube at the bend area. Ovary with two loculus, each containing two eggs, topped by a long style of 3 cm and a cup-shaped stigma with 2 fused lips.
 
Fruit

The fruit is a dehiscent capsule with 2 loculus, a spherical base of about 13 to 18 mm in diameter, surmounted by a thick long beak, 2 to 5 cm long and 7 mm in diameter. At maturity the capsule abruptly opens in two valves, projecting the seeds over long-distance. Each loculus contains two seeds attached to a small appendage having a spring effect.

Seed

The seed is flattened, round, 5 to 10 mm in diameter, with 1 smooth and 1 warty surface.

Origin
 
Thunbergia grandiflora is a species native to South East Asia (Myanmar, Tailand, Viet Nam and China).
 
Worldwide distribution
 
It is now naturalized in tropical regions of Central America, tropical South America, southern USA, tropical and southern Africa, South-west islands of the Indian Ocean (Madagascar, Seychelles, Reunion, Mauritius), India, China, South East Asia, Indonesia, Australia, New caledonia and the Pacific Islands.

https://www.gbif.org/fr/species/5415456