Family: Myrtaceae

Origin, Description & Uses:
Metrosideros excelsa (New Zealand Christmas tree, New Zealand ʻōhiʻa) is a broadleaf evergreen tree native to the coastal regions of New Zealand’s North Island. It is best known for its brilliant red to orange, brush-like flowers that bloom in late spring to summer (around Christmas in its native range), attracting birds and pollinators. The tree has a spreading, often irregular canopy and produces dense, leathery leaves that help it tolerate salty winds and harsh coastal conditions. In landscaping, it is widely valued as an ornamental shade tree and windbreak, especially in coastal gardens and urban plantings in mild climates.

Risks & Threats:
Although Metrosideros excelsa is currently not known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern, including its tolerance of a wide range of environmental conditions, long lifespan, and ability to produce large quantities of viable seed. In suitable environments, these characteristics could allow it to compete with native vegetation and potentially alter plant community structure, particularly in tropical island ecosystems that are sensitive to invasive species. Given Hawaii’s unique native forests and the ecological importance of closely related native ʻōhiʻa species, caution is warranted. When possible, choosing a low-risk or native alternative is strongly recommended to help protect Hawaii’s biodiversity and ecological balance.

High Risk Traits:

• Naturalized in South Africa & Australia
  
• Environmental weed (forms dense thickets in South Africa)
  
• Produces viable seed (99% germination)
  
• Hybridizes naturally with M. robusta
  
• Self-compatible (high levels of self-pollination)
  
• Wind-dispersed seeds
  
• Prolific seed production
  
• Tolerates wide range of soils & climates (USDA zones 9b–11)
  
• Benefits from fire & pruning
  
• Unpalatable to grazing animals (reduces regeneration)

Low Risk Traits:

• No toxicity to humans or animals
  
• No spines, thorns, or burrs
  
• Not shade tolerant (requires full sun)
  
• No bird dispersal or seed bank persistence
  
• Limited vegetative reproduction