Family: Aquifoliaceae

Origin, Description & Uses
Ilex paraguariensis (yerba mate) is a small to medium evergreen tree native to subtropical South America, including Brazil, Argentina, Paraguay, and Uruguay. It typically grows in moist forest understories and can reach 15–20 meters in height in its native range, though it is usually smaller in cultivation. The plant has leathery, serrated leaves and produces small white flowers followed by red to purple berries. Yerba mate is best known for its leaves, which are harvested, dried, and brewed into a caffeinated beverage widely consumed for its stimulating and social qualities. It is also cultivated as a commercial crop and occasionally planted as an ornamental.

Risks & Threats
On Oʻahu, Ilex paraguariensis is naturalized and shows traits that are cause for concern, including bird-dispersed seeds, tolerance of shaded forest conditions, and the ability to establish in understory environments. These characteristics increase its ability to spread beyond planting sites and persist in native and disturbed forests. Once established, it may compete with native vegetation and gradually alter forest composition and structure. Because of these risks, it could detrimentally impact tropical island ecosystems over time, and planting low-risk or native alternatives is strongly recommended to help protect Hawaiʻi’s natural habitats.

High Risk Traits:

• Naturalized beyond native range (e.g., Hawaii, Texas)
  
• Congeneric (other Ilex species) are documented weeds
  
• Allelopathic (inhibits germination/growth of other plants)
  
• Shade tolerant
  
• Tolerates coppicing and mutilation
  
• Bird-dispersed seeds (fleshy fruit)
  
• Seeds survive gut passage
  
• Intentionally dispersed by people (economically important crop)

Low Risk Traits:

• Not a garden, agricultural, or environmental weed (no negative impacts reported)
  
• No spines, thorns, or burrs
  
• Not toxic to animals or humans (used as tea)
  
• Dioecious (requires cross-pollination) – self-incompatible
  
• Low seed viability and slow seed maturation
  
• Narrow soil requirements (acidic soils only)