Family: Aquifoliaceae

Origin, Description & Uses
Ilex dimorphophylla (Okinawan holly) is a small evergreen shrub or tree native to Japan’s Ryukyu Islands. It has dense growth and unique foliage with two leaf shapes, making it popular for hedges, borders, and topiary. It is often used as a warm-climate alternative to boxwood due to its neat form and tolerance to pruning.

Risks & Threats
Okinawan holly is considered low risk in Hawaii and has not shown invasive tendencies. It does not spread aggressively or impact native ecosystems, making it a generally safe choice for landscaping when properly managed.

High Risk Traits:

• Grows in subtropical climates (USDA zones 7b-10b)
  
• Has a history of repeated introductions outside its native range
  
• Congeneric weeds exist (e.g., Ilex aquifolium naturalized in multiple regions)
  
• Produces spines or sharp edges
  
• Tolerates a wide range of soil conditions
  
• Produces viable seed
  
• Hybridizes naturally
  
• Propagules dispersed intentionally by people and by birds
  
• Propagules survive passage through the gut
  
• Forms a persistent seed bank (seeds can take up to 3 years to sprout)

Low Risk Traits:

• No evidence of naturalization or weediness
  
• Not toxic to animals or humans (berries mildly toxic but not a major risk)
  
• Not shade tolerant (requires full sun)
  
• Dioecious (requires both male and female plants for berries)
  
• No vegetative fragmentation
  
• Slow growing (minimum generative time 4+ years)
  
• Propagules not adapted for wind, water, or external animal dispersal