Thunbergia grandiflora
(Bengal trumpet)

Preferred Scientific Name

• Thunbergia grandiflora Roxb.

Preferred Common Name

• Bengal trumpet

Other Scientific Names

• Flemingia grandiflora Rottler
• Thunbergia adenophora W.W. Sm.
• Thunbergia chinensis Merr.
• Thunbergia cordifolia Nees
• Thunbergia lacei Gamble

International Common Names

• English: Bengal clock vine; Bengal trumpet vine; blue thunbergia; blue trumpet vine; large thunbergia; sky vine; skyflower vine; trumpet vine
• Spanish: brisa de la mañana; corona de rey; faurestina; fausto; pompeya; tumbergia azul
• French: liane de chine; liane mauve

Local Common Names

• Australia: blue sky vine; blue trumpet
• Dominican Republic: ristra de ajo
• Micronesia, Federated states of: iolen pengkal (Pohnpei)
• Palau: bung el etiu
• Samoa: palulu

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Scrophulariales
•                         Family: Acanthaceae
•                             Genus: Thunbergia
•                                 Species: Thunbergia grandiflora

The family Acanthaceae includes about 4000 species widespread in both New and Old World Tropics. This family includes a range of morphological diversity, habitats, and biogeographic patterns. Many species within the family are commonly used as ornamentals including species in the genera Justicia, Peristrophe, Ruellia, and Thunbergia (Liogier, 1988; Stevens, 2012). The genus Thunbergia includes about 90 species of herbaceous or woody vines, and less often shrubs of paleotropical origin (Stevens, 2012). The species T. alata, T.fragrans, and T. laurifolia have also been described as invasive species in tropical and subtropical regions of the world (PIER, 2012; Randall, 2012).

Perennial, woody vine, 10-20 m in length. Stems are cylindrical, up to 2.5 cm in diameter, striate, puberulous; cross section of the stem with the pith hollow and the xylem tissue with wide rays. Leaves are opposite; blades 15-26 × 13-30 cm, ovate or broadly ovate, chartaceous, the apex acute or acuminate, the base cordiform, the margins lobate-dentate, ciliate; upper surface is dark green, shiny, puberulous, with slightly prominent venation; lower surface is light green, dull, glabrous or puberulous, with prominent venation; petioles 6-12 cm long. Flowers are arranged in axillary cymes; pedicels robust, cylindrical, 4-6 cm long; bracts light green, ovate, approximately 4 cm long, covering the calyx and the corolla tube. The calyx is green with the form of a ring, 4-5 mm long; corolla lilac-blue or white, with 5 lobes, the tube 6-7 cm long, light yellow inside, narrow at the base, the limb 6-7 cm in diameter. Fruits are capsules, approximately 3 cm long, subglobose at the base, the upper half in the form of a beak, explosively dehiscent in two halves (Acevedo-Rodríguez, 2005).

T. grandiflora was probably introduced as an ornamental in the Caribbean Region late in the nineteenth century. It appears in an 1892 herbarium collection made by A. Duss on Guadeloupe Island (Smithsonian Herbarium Collection). Later, Ignaz Urban in his book Symbolae Antillanae reported this species as “cultivated in gardens and escaped” for the islands of Cuba, Guadeloupe, Dominica, Martinique, and St. Vincent (Urban, 1901). T. grandiflora was also reported as commonly planted in gardens by N.L. Britton in Bermuda in 1918 (Britton, 1918) and in Puerto Rico and Virgin Islands in 1925 (Britton and Wilson, 1925). During the 1990s this species has been collected in Puerto Rico from naturalized individuals from widespread localities (Acevedo-Rodríguez, 2005). In Hawaii, T. grandiflora was first collected in 1937 on O'ahu and it is now spreading along hiking trails or margins of urban areas, at least on Kaua'i, O'ahu, Maui, and Hawaii (Wagner et al., 1999; Starr et al., 2003).

Soil drainage

• free

Soil reaction

• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• shallow

T. grandiflora reproduces sexually by seeds and vegetatively by stem fragments, tubers, and roots (Starr et al., 2003; ISSG, 2012; PIER, 2012). Seeds are catapulted several metres when ripe pods open and they can also be dispersed by rivers, streams and on waterways after rain storms (Queensland Department of Primary Industries and Fisheries, 2007). T. grandiflora also spreads by underground tubers and roots that easily re-spread producing new plants. Fragments of stems and roots may be dispersed to new locations by humans, livestock, vehicles, and/or floodwaters. Tubers and roots can also be spread by the movement of soil (Starr et al., 2003; BioNET-EAFRINET, 2011; ISSG, 2012; PIER, 2012).

T. grandiflora has an extensive tuberous root system, which can weigh up to 70 kg and can damage river banks, paths, fences and building foundations (Motooka et al., 2003). This fast-growing vine forms dense colonies that engulf native vegetation, climbing high into forest canopies and shading-out vegetation in the understory of native forests. For example, in some areas in Australia this species can cover 100% of the vegetation (Queensland Department of Primary Industries and Fisheries, 2007). It also impacts negatively on the germination and establishment of seedlings of native plants and the weight of the stems can kill host- trees (BioNET-EAFRINET, 2011; ISSG, 2012). In Australia, T. grandiflora is a serious environmental problem. It is affecting agricultural lands and it is a serious danger to the survival of small remnants of the threatened lowland tropical rainforest in the areas of Queensland that have been fragmented by agricultural and urban development (Queensland Department of Primary Industries and Fisheries, 2007).

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Long lived
• Fast growing
• Has high reproductive potential
• Reproduces asexually

• Ecosystem change/ habitat alteration
• Host damage
• Infrastructure damage
• Monoculture formation
• Reduced native biodiversity
• Threat to/ loss of native species

• Competition - monopolizing resources
• Competition - shading
• Competition - smothering
• Competition - strangling
• Rapid growth
• Rooting

• Highly likely to be transported internationally deliberately

T. grandiflora is an economically important species widely cultivated as an ornamental and as a hedge plant in tropical and subtropical regions (Starr et al., 2003). This species is still sold in nurseries and is commonly planted to cover fences and walls in gardens in warm climates. In addition, T. grandiflora is used as a medicinal plant in traditional medicine in Asia and Africa. In Tropical Africa (Tanzania and Uganda), it has been used as a source of green manure and for fuelwood (Bio-NET-EAFRINET, 2011).