Family: Fabaceae

Origin, Description & Uses
Tephrosia purpurea is a perennial herb or small subshrub native to a broad region extending from Africa and the Arabian Peninsula through tropical and subtropical Asia to the South Pacific. It typically grows 1–3 feet (0.3–1 m) tall and has slender stems, gray-green compound leaves, and small pink to purple pea-like flowers followed by narrow seed pods. The species has been used in traditional medicine, as a green manure and nitrogen-fixing cover crop, for erosion control, and in some regions as a natural fish poison or botanical insecticide due to compounds found in its tissues.

Risks & Threats
Tephrosia purpurea is naturalized on Niʻihau, Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi Island. It possesses traits that are cause for concern, including prolific seed production, nitrogen-fixing ability, tolerance of dry and disturbed environments, and the capacity to establish persistent populations. These characteristics allow it to spread into open habitats, roadsides, pastures, and dry natural areas, where it may compete with native vegetation and alter soil conditions, potentially detrimentally impacting tropical island ecosystems. Because this species is already widespread in Hawaiʻi, it is recommended that existing populations be managed and that planting or intentional spread into areas where it is not yet widely established be avoided to minimize further negative impacts. When selecting plants for landscaping or restoration, consider choosing a low-risk or native alternative whenever suitable options are available.

High Risk Traits:

• Naturalized in Hawaii, Okinawa, and Ryukyu Islands
  
• Naturalized across all main Hawaiian Islands (Niʻihau, Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, Hawaiʻi)
  
• Agricultural weed in Sri Lanka
  
• Congeneric (T. uniflora) is a major weed
  
• Contains fish toxin (tephrosin) and is cytotoxic
  
• Host to multiple fungal pathogens
  
• Potential fire hazard in dense dryland patches
  
• Tolerates diverse soils (sand, gravel, coal waste)
  
• Nitrogen-fixing, competes in low-nutrient soils
  
• Persistent soil seed bank (>1 year) due to hard seed coat
  
• Short generation time (annual)
  
• Intentionally spread by humans for land rehabilitation

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not parasitic or allelopathic
  
• Not toxic to mammals
  
• Not shade-tolerant
  
• No vegetative reproduction
  
• No accidental dispersal (no attachment structures)
  
• Large seeds – not likely seed contaminants
  
• Limited wind/water dispersal; dryland species
  
• Not bird-dispersed (no confirmed gut passage)
  
• Low seed production (few seeds per pod)
  
• Controllable with herbicides (e.g., 2,4-D)