Family: Hydrocharitaceae

Origin, Description & Uses:
Hydrocharis laevigata (commonly known as Amazon frogbit or South American spongeplant) is native to Mexico and tropical regions of Central and South America. It is a free-floating aquatic plant that forms small rosettes of rounded, glossy leaves that float on the water surface. The plant produces trailing stolons with spongy, air-filled tissues that help it stay buoyant. Because of its attractive appearance and rapid growth, it is sometimes used in ornamental water gardens, ponds, and aquariums, where it can provide shade and help absorb excess nutrients from the water.

Risks & Threats:
Although Hydrocharis laevigata is currently not known to be naturalized in the Hawaiian Islands, it does possess traits that are cause for concern, including rapid vegetative reproduction and the ability to form dense floating mats. In other regions, similar aquatic plants have become invasive, blocking sunlight, reducing oxygen levels in the water, and outcompeting native aquatic species. These impacts can disrupt freshwater ecosystems, harm wildlife habitat, and interfere with water flow and management. Because of these risks, it is important to avoid introducing this species to Hawaii, and to choose low-risk or native alternatives better suited for tropical island aquatic environments.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Grows in tropical climates
  
• Naturalized in California, Australia, Japan and possibly elsewhere
  
• An environmental weed
  
• Limnobium spongia also invasive
  
• Can form dense stands in aquatic systems and impede the flow of water
  
• Reproduces by seeds and vegetatively
  
• Seeds and vegetative fragments dispersed by water, stuck to boats and animals, intentionally by people, and internally by animals
  
• Seeds persist for 4 or more years
  
• Mechanical damage and control efforts can contribute to spread of viable vegetative fragments

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Non-toxic
  
• Ornamental
  
• Several herbicides provide effective control