Family: Nephrolepidaceae

Origin, Description & Uses
Nephrolepis biserrata, commonly known as fishtail fern or giant sword fern, is a large tropical fern native to warm regions throughout the tropics and subtropics. It is valued for its long, arching fronds with finely divided leaflets that create a lush, tropical appearance in gardens and landscapes. This fern is often grown as an ornamental plant in shaded outdoor areas, hanging baskets, and interiorscapes because of its vigorous growth and attractive foliage. In tropical climates it is also used as a groundcover or erosion-control plant in moist, shaded locations.

Risks & Threats
Although Nephrolepis biserrata 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 if introduced or unmanaged. This fern spreads readily through creeping rhizomes and dense growth, allowing it to form thick mats that may crowd out native vegetation and alter understory habitats. Its ability to thrive in warm, humid environments increases the risk that it could establish in sensitive forest or riparian areas. Because of these concerns, it is recommended that gardeners and landscapers choose low risk or native fern alternatives when suitable options are available.

High Risk Traits:

• Naturalized beyond native range
  
• Garden/amenity weed (invasive, forms large colonies)
  
• Agricultural weed (spores dominate soil seed bank)
  
• Congeneric weed (N. multiflora displaces vegetation)
  
• Shade tolerant
  
• Tolerates wide range of soil pH and types
  
• Forms dense, impenetrable thickets
  
• Produces viable spores
  
• Hybridizes naturally
  
• Reproduces by vegetative fragmentation (rhizomes, stolons)
  
• Fast growth rate (generative time ~1-2 years)
  
• Propagules dispersed by wind, water, intentionally by people
  
• Prolific spore production (>90% of viable propagules in soil samples)
  
• Tolerates mutilation, cultivation, fire (recovers quickly after fire)

Low Risk Traits:

• No spines, thorns, or burrs
  
• Palatable to grazing animals (eaten by sheep, goats)
  
• Non-toxic to cats, dogs, horses; no evidence of toxicity to humans
  
• Controlled by herbicides (glyphosate effective)