Family: Fabaceae

Origin, Description & Uses
Neustanthus phaseoloides, commonly known as tropical kudzu, is native to tropical and subtropical regions of Asia. It is a fast-growing, perennial, twining vine in the legume family that can form dense mats over vegetation and open ground. The plant produces vigorous leafy growth and purple to lavender pea-like flowers, followed by seed pods typical of legumes. Tropical kudzu has been used in some regions as a forage crop, green manure, and cover crop due to its ability to fix nitrogen and rapidly improve soil fertility and ground cover.

Risks & Threats
Tropical kudzu is naturalized on Oʻahu and Maui and possesses traits that are cause for concern, including extremely rapid growth, aggressive climbing habit, and nitrogen-fixing ability that can alter soil chemistry. It can smother and outcompete native vegetation by engulfing shrubs and trees, forming dense mats that block sunlight and suppress native plant regeneration. Once established, it is difficult to control and can spread into forests, disturbed areas, and conservation lands, posing a serious threat to tropical island ecosystems. Because of these impacts, tropical kudzu could detrimentally affect Hawaiʻi’s ecosystems where it continues to spread. Choosing low-risk or native alternatives is strongly recommended when available. In areas where it is not yet widely established, prevention and careful management are especially important to minimize further spread and ecological damage.

High Risk Traits:

• Naturalized beyond native range
  
• Naturalized on O'ahu and Maui
  
• Agricultural weed (e.g., Brazil, Galapagos, Hawaii)
  
• Host for recognized pests (e.g., oil palm leaf miner)
  
• Shade tolerant
  
• Tolerates wide range of soil conditions
  
• Climbing/smothering growth habit
  
• Geophyte (tuberous roots)
  
• Produces viable seed
  
• Self-compatible
  
• Reproduces by vegetative fragmentation (runners)
  
• Minimum generative time ≤1 year
  
• Propagules likely dispersed unintentionally (seed contaminant)
  
• Propagules dispersed intentionally by people (forage/fallow)
  
• Propagules survive passage through gut (hard seed coat)
  
• Prolific seed production (>1000/m²)
  
• Forms persistent seed bank (>1 yr)
  
• Tolerates mutilation/cutting

Low Risk Traits:

• Palatable to grazing animals
  
• Not toxic to animals or humans
  
• No evidence of allelopathy or spines/thorns
  
• Not a fire hazard (requires wet conditions)
  
• Well controlled by herbicides
  
• Effective natural enemies present locally (e.g., pod-borers)