Family: Fabaceae

Origin, Description & Uses:
Crotalaria juncea, commonly known as Indian hemp or sunn hemp, is a fast-growing leguminous plant native to India and other parts of tropical Asia. It is typically grown as a tall, upright annual with bright yellow flowers and soft, fibrous stems. Globally, Indian hemp is widely used as a cover crop and green manure because it improves soil fertility, suppresses weeds, and helps reduce erosion through nitrogen fixation. It has also been used for fiber production and, in some settings, for forage or soil restoration projects.

Risks & Threats:
In Hawaiʻi, Crotalaria juncea is naturalized and does possess traits that are cause for concern, including rapid growth and the ability to spread in disturbed areas. While it is often intentionally planted for agricultural purposes, these characteristics mean it has the potential to move beyond cultivation and interact with surrounding vegetation. Caution is recommended to ensure that it will not negatively impact Hawaiʻi’s ecosystems, particularly in or near natural areas. When possible, choosing low-risk or native alternatives can help reduce the potential for unintended ecological impacts while still meeting soil improvement or restoration goals.

High Risk Traits:

• Naturalized on Oahu, East Maui, Hawaiian Islands, China, and elsewhere
  
• Broad climate suitability and thrives in tropical climates
  
• Potentially weedy
  
• Other Crotalaria species documented to be invasive
  
• Potentially toxic (although Hawaiian cultivar 'Tropics Sun' reportedly non-toxic)
  
• Tolerates many soil conditions (and potentially able to exploit many different habitat types)
  
• Capable of self-pollination
  
• Reaches maturity in <1 year
  
• Can tolerate repeated harvesting after 6-8 weeks of growth

Low Risk Traits:

• Evidence of weediness or negative impacts unspecified or unverified
  
• Palatable to ungulates
  
• Useful as a green manure and cover crop to exclude weeds
  
• Used as a green fire break
  
• Shade-intolerant
  
• Seeds apparently do not persist in the soil
  
• Pods and seeds rely on human transport for dispersal