Family: Myrtaceae

Origin, Description & Uses
Eucalyptus macrocarpa, commonly known as mottlecah, is a striking ornamental tree native to the southwestern regions of Australia. It is best known for its large, silvery-blue, rounded leaves and exceptionally showy flowers, which can reach several inches across and range in color from deep red to pink. This small, often multi-stemmed tree or shrub has a sculptural appearance and thrives in well-drained soils and sunny conditions. Due to its dramatic foliage and flowers, mottlecah is widely cultivated in gardens and landscapes as an ornamental specimen, particularly in dry or Mediterranean-style plantings.

Risks & Threats
Although Eucalyptus macrocarpa is not currently known to be naturalized in the Hawaiian Islands, it does possess traits that may be cause for concern. Like many eucalyptus species, it is adapted to dry environments, can tolerate poor soils, and may establish in disturbed areas. Some eucalyptus species also produce abundant seed and can alter soil conditions or fire regimes. While there is no clear evidence of invasiveness at this time, these characteristics suggest a potential risk if introduced more widely. Further evaluation is needed to determine whether mottlecah could spread or negatively impact native ecosystems in Hawaii.

High Risk Traits:

• Congeneric weed: Other Eucalyptus species are invasive.
  
• Hybridizes naturally: Known to hybridize with other eucalypts.
  
• Intentional dispersal: Seeds and plants are commercially available.
  
• Wind dispersal: Propagules are adapted for dispersal by wind.
  
• Tolerates mutilation: Resprouts from lignotuber after cutting or fire.

Low Risk Traits:

• No naturalization: No evidence of naturalizing outside native range.
  
• No weed history: Not documented as a garden, agricultural, or environmental weed.
  
• Limited climate suitability: Unreliable in subtropical climates.
  
• No toxicity: Not toxic to humans or animals.
  
• No physical defenses: Lacks spines, thorns, or burrs.
  
• Not shade tolerant: Requires open conditions.
  
• No animal dispersal: Seeds dispersed by wind, not birds or other animals.
  
• No vegetative spread: Does not spread via underground storage organs.