Family: Menyanthaceae

Origin, Description & Uses:
Nymphoides geminata (entire marshwort, yellow water snowflake) is an aquatic plant native to eastern Australia. This floating freshwater species is known for its rounded green leaves that resemble small water lilies and its bright yellow, fringed flowers that rise above the water surface. It grows in ponds, wetlands, slow-moving waterways, and other shallow aquatic habitats. Because of its attractive appearance and ability to spread across the water surface, it is sometimes cultivated as an ornamental plant for water gardens and ponds.

Risks & Threats:
Although Nymphoides geminata is not currently known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern and could detrimentally impact tropical island ecosystems. Like other floating aquatic plants, it can spread rapidly in suitable wet habitats, forming dense mats that shade native aquatic vegetation, reduce oxygen levels in the water, and alter habitat conditions for native fish and wildlife. Aquatic invasive plants can also clog waterways and create management challenges in wetlands and irrigation systems. Due to these potential risks, caution is advised when considering this species for cultivation in Hawaii. Choosing a low risk or native alternative is recommended whenever suitable options are available.

High Risk Traits:

• Broad climate suitability
  
• Naturalized outside native range
  
• Recorded as an environmental weed
  
• Congeneric weed exists
  
• Shade tolerant
  
• Tolerates wide range of soil conditions
  
• Climbing or smothering growth habit
  
• Forms dense thickets
  
• Aquatic (facilitates spread)
  
• Produces viable seed
  
• Self-compatible or apomictic
  
• Reproduces by vegetative fragmentation
  
• Minimum generative time ≤1 year
  
• Propagules dispersed unintentionally (e.g., traffic areas)
  
• Propagules dispersed intentionally by people
  
• Propagules water-dispersed
  
• Tolerates mutilation, cultivation, or fire

Low Risk Traits:

• Not a weed of agriculture/forestry/horticulture
  
• No spines, thorns, or burrs
  
• Not toxic to animals or humans
  
• No fire hazard
  
• Not wind-dispersed, bird-dispersed, or animal externally-dispersed
  
• No propagule gut passage survival
  
• Not highly prolific seed producer (<1000/m²)
  
• Well controlled by herbicides