Family: Brassicaceae

Origin, Description & Uses
Eutrema japonicum, commonly known as Japanese horseradish or wasabi, is a perennial plant native to mountain streams of Japan. It grows best in cool, shaded, and moist environments, producing thick, green rhizomes that are grated to make the pungent, spicy condiment famously used with sushi and other Japanese dishes. The plant also features small, heart-shaped leaves and clusters of tiny white flowers in spring, adding a mild ornamental appeal. Beyond culinary uses, wasabi has been used in traditional medicine for its potential antibacterial and anti-inflammatory properties.

Risks & Threats
Eutrema japonicum is considered low risk in Hawaii as it is not known to naturalize or spread aggressively in local ecosystems. It prefers very specific growing conditions—shaded, wet, and cool areas—making it unlikely to outcompete native plants. While gardeners should still monitor for pests or fungal issues in cultivation, Eutrema japonicum does not pose a significant threat to Hawaii’s natural habitats and can be enjoyed safely as a specialty garden or culinary plant.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Naturalized in Taiwan and possibly elsewhere
  
• Regarded as invasive in lakeshores and riparian habitats, although impacts are unspecified
  
• May be a skin irritant to susceptible individuals
  
• Shade-tolerant
  
• Reproduces by seeds and vegetatively by rhizomes
  
• Seeds likely dispersed by water, adhering to surfaces, and intentionally by cultivation
  
• Seeds exhibit dormancy, but lose viability if dried
  
• May be able to coppice and resprout after cutting

Low Risk Traits:

• Domesticated since about 10th century
  
• Although reported as invasive, no impacts have been specified
  
• Unarmed (no spines, thorns or burrs)
  
• Valuable food plant
  
• Self-incompatible
  
• Seeds lose viability if dried