Family: Lamiaceae

Origin, Description & Uses
Spearmint (Mentha spicata) is native to a wide region spanning Europe to China and is now widely grown around the world. It is a fast-growing, aromatic perennial herb in the mint family, known for its bright green, serrated leaves and refreshing scent. Spearmint is commonly used in teas, culinary dishes, desserts, and herbal remedies, and is popular in home gardens for its fragrance and ease of growth. In Hawaiʻi, it is cultivated in gardens and occasionally escapes into surrounding areas, particularly in mesic environments at elevations up to about 1,600 meters on Oʻahu and Hawaiʻi Island.

Risks & Threats
Although often valued as a useful herb, spearmint is naturalized in Hawaiʻi and possesses traits that are cause for concern. It spreads aggressively through underground rhizomes and can quickly form dense mats that crowd out native vegetation and reduce habitat quality. In moist, fertile environments typical of tropical islands, it can persist and expand beyond cultivation, especially where gardens border natural areas. If left unmanaged, it could detrimentally impact tropical island ecosystems by displacing low-growing native plants and altering understory plant communities. Careful cultivation is recommended to prevent escape, and gardeners are encouraged to choose low-risk or native alternatives when available to support Hawaiʻi’s unique ecosystems.

High Risk Traits:

• Broad climate suitability
  
• Widely naturalized (including Oahu and Hawaii islands)
  
• Garden and disturbance weed
  
• Potential environmental weed
  
• Other Mentha species have become invasive
  
• Possesses allelopathic properties
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Can form monocultures and possibly exclude other vegetation
  
• Hybridizes with other Mentha species
  
• Self-compatible
  
• Spreads vegetatively
  
• Seeds and vegetative fragments can be spread by water, or by clinging to animals or machinery
  
• Can resprout from rhizomes following the removal of the aboveground growth

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Ornamental and culinary uses
  
• May produce few or no seeds in introduced range