Family: Hydrocharitaceae

Origin, Description & Uses
Hydrocharis morsus-ranae, commonly known as common frogbit or European frog’s-bit, is a free-floating aquatic plant native to Europe, parts of Asia, and northern Africa. It resembles a small water lily, with round, glossy leaves that float on the water’s surface and delicate white, three-petaled flowers that bloom in warm months. The plant forms dense mats connected by stolons and produces small overwintering buds (turions) that allow it to survive unfavorable conditions. Because of its attractive appearance and ability to provide shade and shelter in ponds, frogbit is sometimes used in ornamental water gardens and aquaria.

Risks & Threats
Although this species is currently not known to be naturalized in the Hawaiian Islands, it does possess traits that are cause for concern, and which could detrimentally impact tropical island ecosystems. Frogbit can spread rapidly across still or slow-moving water, forming thick mats that block sunlight, reduce oxygen levels, and outcompete native aquatic plants. These dense infestations can degrade water quality, alter habitat for fish and invertebrates, and impede water flow. Its ability to reproduce vegetatively and survive via turions makes it especially difficult to control once established. It is recommended to choose a low risk or native alternative to help prevent potential escape and ecological harm.

High Risk Traits:

• Broad climate suitability
  
• Naturalized in North America from Ottawa, Montreal, Lake Ontario, Quebec City, central and southwestern parts of southern Ontario, and northern New York, Vermont and eastern Michigan
  
• A weed of aquatic habitats that can impact fisheries, recreation, and biodiversity
  
• Other Hydrocharis species have become weeds
  
• Smother water surfaces
  
• Forms dense mats
  
• Reproduces by weeds and vegetatively
  
• Can reproduce in one growing season
  
• Seeds and vegetative parts dispersed by water, intentionally by people, attached to boats, waterbirds, and possibly internally by birds
  
• Vegetative propagules (turions) may persist over one growing season

Low Risk Traits:

• Primarily in temperate climates. May only be invasive at higher elevations of tropical climates
  
• Unarmed (no spines, thorns or burrs)
  
• Palatable to aquatic animals
  
• Dioecious or self-incompatible
  
• Herbicides may provide effective control