Family: Myrtaceae

Origin, Description & Uses
Eucalyptus saligna, commonly known as Sydney blue gum, is native to eastern Australia. It is a tall, fast-growing evergreen tree that can reach heights of 40–60 meters (130–200 feet) in its native range, with smooth, grayish bark that sheds in patches and lance-shaped glossy green leaves. The tree produces clusters of white flowers and woody capsules that contain numerous small seeds. Sydney blue gum is valued for its timber, which is used in construction, furniture, and paper production, and it is sometimes planted for shade or ornamental purposes.

Risks & Threats
In Hawaii, Eucalyptus saligna is naturalized on Kaua‘i, Moloka‘i, Maui, and Hawai‘i islands. It possesses traits that raise ecological concerns, including rapid growth, prolific seed production, and the ability to form dense stands that outcompete native vegetation. Its flammable litter and canopy can also increase wildfire risk, which is especially dangerous in tropical island ecosystems. Because of these impacts, planting Sydney blue gum is discouraged. Choosing a low-risk or native tree alternative is recommended to protect Hawaii’s unique ecosystems.

High Risk Traits:

• Naturalized in Hawaii and New Zealand
  
• Congeneric Eucalyptus species are significant weeds
  
• Broad climate suitability (wide altitude, temperature, and rainfall tolerance)
  
• Extensive history of repeated introductions for forestry
  
• Allelopathic effects on other plants
  
• Tolerates a wide range of soil types
  
• Produces viable seed
  
• Hybridizes naturally with other Eucalyptus species
  
• Self-compatible (outcrossing rate of 77%)
  
• Wind-dispersed seeds
  
• Intentionally spread by people for timber and shelterbelts
  
• Prolific seed production (tiny seeds, ~460 per gram)
  
• Resprouts vigorously after cutting or fire (lignotuber and epicormic buds)

Low Risk Traits:

• Not documented as a garden, agricultural, or environmental weed
  
• Lacks spines, thorns, or burrs
  
• Not parasitic, toxic, or a fire hazard
  
• No major pest or pathogen issues
  
• Shade intolerant
  
• Does not form dense thickets
  
• No vegetative spread in the wild
  
• Not dispersed by water, birds, animals, or as a crop contaminant