Family: Acanthaceae

Origin, Description & Uses:
Black-eyed Susan (Thunbergia alata) is a fast-growing twining vine native to tropical and southern Africa and Madagascar. It is widely cultivated as an ornamental for its cheerful yellow, orange, cream, or white flowers with distinctive dark centers, as well as its ability to quickly cover fences, trellises, arbors, and hanging baskets. Its long blooming season, attractive foliage, and ease of cultivation have made it a popular choice in tropical and subtropical gardens around the world.

Risks & Threats:
Black-eyed Susan is naturalized on Kauaʻi, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi Island, and is potentially naturalizing on Oʻahu. This species possesses traits that are cause for concern, including rapid growth, prolific seed production, and the ability to spread beyond cultivation. It can form dense mats that smother native vegetation, outcompete other plants for sunlight and space, and detrimentally impact tropical island ecosystems. Birds, water, and human activities can help disperse its seeds, allowing it to establish in disturbed habitats and natural areas. Where possible, choose a low-risk or native climbing vine instead. In areas where black-eyed Susan is already widespread, avoid planting it near forests, streams, or other natural habitats, and manage existing plants to prevent further spread into uninfested areas.

High Risk Traits:

• Naturalized and invasive in Hawaii, Australia, and elsewhere
  
• Naturalized or potentially naturalizing on all main Hawaiian Islands: Kauaʻi (naturalized), Oʻahu (potentially naturalizing), Molokaʻi (naturalized), Lānaʻi (naturalized), Maui (naturalized), and Hawaiʻi (naturalized)
  
• Native to tropical/subtropical climates
  
• Repeated introductions as an ornamental
  
• Congeneric species are serious weeds
  
• Climbing vine that smothers vegetation
  
• Shade tolerant
  
• Self-compatible (self-fertile)
  
• Reproduces via vegetative fragments
  
• Annual; flowers within one year
  
• Widely dispersed intentionally by people
  
• Escapes gardens via dumping
  
• Tolerates cutting and resprouts

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not toxic to humans or animals (edible, used as fodder)
  
• Palatable to grazers
  
• No wind, water, or bird dispersal (seeds ejected mechanically)