Family: Acanthaceae

Origin, Description & Uses
White thunbergia (Thunbergia fragrans), also known as sweet clockvine, is a twining perennial vine native to the Indian Subcontinent, southern China, Indochina, and the Philippines. It is valued as an ornamental for its attractive white, trumpet-shaped flowers with yellow throats, glossy green foliage, and long blooming season. This fast-growing vine is commonly planted on trellises, fences, arbors, and other garden structures, where it provides quick screening and ornamental appeal in tropical and subtropical landscapes.

Risks & Threats
White thunbergia is naturalized on Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi Island. It possesses traits that are cause for concern, including rapid growth, vigorous climbing stems, and the ability to spread beyond cultivation. The vine can smother shrubs, young trees, and other vegetation, forming dense tangles that compete with native plants for sunlight and space. These characteristics can detrimentally impact tropical island ecosystems, particularly in disturbed forests, roadsides, and unmanaged natural areas. Because this species is already widespread in Hawaiʻi, it should be carefully managed and its use avoided in areas where it is not yet widely established to help prevent further spread. Whenever possible, choose a low-risk or native vine as an alternative for landscaping.

High Risk Traits:

• Naturalized in Fiji, Taiwan, and other regions
  
• Naturalized on Kaua'i, O'ahu, Molokai, Lana'i, Maui, and Hawai'i
  
• Agricultural weed (papaya fields)
  
• Congener (T. grandiflora) is highly invasive
  
• Wide climate tolerance (sea level to 4,000 ft; USDA zones 10–11)
  
• Tolerates acidic, alkaline, sandy, loamy, and clay soils
  
• Twining vine; smothers other vegetation
  
• Produces viable seeds (viable for 2–3 years)
  
• Reproduces vegetatively (cuttings, stem/root fragments)
  
• Fast growth rate
  
• Widely cultivated as ornamental (intentional human dispersal)
  
• Responds vigorously to pruning

Low Risk Traits:

• No spines, thorns, or burrs
  
• Non-toxic to humans and animals
  
• Not shade-tolerant (prefers full sun)
  
• Limited accidental dispersal (not by wind, water, birds, or external animal attachment)