Family: Fabaceae

Origin, Description & Uses:
Blue rattleweed (Crotalaria verrucosa), also known as blue-flower rattlepod, is a flowering legume native to tropical regions of Africa and parts of Asia. It is a shrubby, fast-growing plant recognized for its showy blue to violet pea-like flowers and distinctive inflated seed pods that rattle when dry. Because it fixes nitrogen in the soil, it has been used in some regions as a green manure, cover crop, or ornamental planting, and it has also been associated with traditional medicinal uses. Its attractive flowers and ability to thrive in warm climates have contributed to its spread beyond its native range.

Risks & Threats:
In Hawaiʻi, blue rattleweed is already naturalized on Kauaʻi and Oʻahu and is potentially naturalizing on Molokaʻi. This species possesses several traits that are cause for concern, including rapid growth, abundant seed production, and the ability to alter soil nutrients through nitrogen fixation. These characteristics can allow it to outcompete native plants and disrupt sensitive tropical island ecosystems. Like other Crotalaria species, it may also contain compounds that are toxic to livestock and wildlife. Due to its current spread and potential ecological impacts, choosing a low-risk, non-invasive, or native alternative is strongly recommended to help protect Hawaiʻi’s unique natural environments.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Thrives in tropical climates
  
• Widely naturalized, including Oahu, and possibly Molokai (Hawaiian Islands)
  
• Weedy plant, potential crop weed
  
• Other species have become invasive
  
• Toxic to animals and people
  
• Host of soybean rust pathogen
  
• Shade-tolerant
  
• N-fixing (may alter soil chemistry)
  
• Reproduces by seed
  
• Self-pollinating
  
• Able to reach maturity in one growing season
  
• Seeds lack a dispersal mechanism, but are likely moved by water when grown in riparian areas
  
• Forms a persistent seed bank

Low Risk Traits:

• Unarmed (no spines, thorns, or burrs)
  
• Palatable despite reports of toxicity
  
• Not reported to spread vegetatively
  
• Herbicides may provide effective control
  
• Mechanical control effective in low densities and for young plants