Family: Fabaceae

Origin, Description & Uses
Indigofera zollingeriana, commonly known as neel, is a fast-growing shrub or small tree in the legume family with a native range extending from Assam through the Nansei-shōtō (Ryukyu Islands) to Borneo. It has soft, feathery compound leaves and produces small pink to reddish-purple pea-like flowers, followed by narrow seed pods. This species is widely valued in tropical agriculture and agroforestry, where it is used as a high-protein forage for livestock, as well as for green manure and soil improvement due to its ability to fix nitrogen. It is also sometimes planted for erosion control or as a cover crop.

Risks & Threats
This species is considered low risk and is not known to be invasive or to significantly disrupt natural ecosystems. Although Indigofera zollingeriana can grow quickly and reproduce by seed, there is little evidence that it spreads aggressively or outcompetes native vegetation. As with any introduced plant, responsible management is recommended to prevent unintended spread into natural areas. Overall, it is unlikely to pose a significant threat to Hawaii’s ecosystems when properly managed.

High Risk Traits:

• Naturalized beyond native range (India)
  
• Congeneric weeds exist (e.g., I. arrecta, I. hendecaphylla)
  
• Nitrogen-fixing woody plant
  
• Produces viable seed; easy to propagate
  
• Likely forms persistent seed bank (hard-seeded legume)
  
• Grows quickly; short generation time
  
• History of repeated introductions (Java, India, Philippines, Jamaica)

Low Risk Traits:

• Narrow climate tolerance (no cold, <500 m elevation)
  
• Not a weed (garden, agricultural, or environmental)
  
• No spines, thorns, burrs, or allelopathy
  
• Not a vine or thicket-forming
  
• No vegetative fragmentation
  
• Propagules not adapted for wind, water, or external animal dispersal
  
• Palatable to grazing animals; no human toxicity
  
• Fire kills plants (though seeds may regenerate)