Family: Fabaceae

Origin, Description & Uses
Neptunia oleracea (sensitive neptunia, water mimosa) is a semi-aquatic tropical plant native to tropical and subtropical regions around the world. It is a fast-growing member of the pea family that typically floats on water or grows in wet soils along ponds, canals, and marshes. The plant is recognized for its feathery foliage and sensitive leaves, which fold inward when touched, similar to other “sensitive plants.” It also produces small yellow flower clusters and buoyant, spongy stems that help it spread across the water surface. In parts of Asia and other tropical regions, water mimosa is cultivated as a leafy vegetable and is sometimes used as livestock forage or in traditional medicine.

Risks & Threats
Although Neptunia oleracea is currently not known to be naturalized in the Hawaiian Islands, it possesses several traits that are cause for concern and could detrimentally impact tropical island ecosystems if introduced or allowed to spread. This species grows rapidly in warm, wet environments and can form dense floating mats that block sunlight, reduce oxygen levels in waterways, impede water flow, and displace native aquatic vegetation. Its ability to reproduce and spread vegetatively from stem fragments increases the risk of accidental establishment in wetlands, streams, taro patches, and other freshwater habitats. Dense infestations could negatively affect water quality, native biodiversity, and wetland function. Because of these invasive characteristics, it is recommended that gardeners, landscapers, and growers choose low-risk or native alternatives whenever suitable options are available.

High Risk Traits:

• Thrives in tropical climates
  
• Naturalized in Australia and elsewhere (origins uncertain)
  
• Environmental Weed of freshwater aquatic habitats
  
• Other Neptunia species have become invasive
  
• Chokes and smothers water surfaces
  
• Reproduces by seeds and spreads by vegetative fragments
  
• Seeds and fragments dispersed by water and by adhering to mud on vehicles
  
• Seeds may form a persistent seed bank
  
• Viable seeds passed through guts of livestock
  
• Able to regrow after cutting and mechanical control

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Provides fodder for livestock
  
• Non-toxic
  
• Consumed by humans as a vegetable, and has medicinal uses
  
• Herbicides may provide effective control