Family: Myrtaceae

Origin, Description & Uses
Melaleuca alternifolia, commonly known as narrow leaf paperbark, narrow leaf teatree, or teatree, is a small evergreen tree native to coastal regions of Queensland and northeastern New South Wales, Australia. It typically grows in moist soils and swampy habitats and is recognized for its narrow aromatic leaves, papery bark, and clusters of small white flowers. This species is widely cultivated for the production of tea tree oil, an essential oil valued in soaps, cosmetics, cleaning products, and traditional herbal remedies for its antimicrobial properties. It is also occasionally planted as an ornamental or windbreak tree in tropical and subtropical landscapes.

Risks & Threats
Although Melaleuca alternifolia is currently not known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern. Like other members of the Melaleuca genus, it is adapted to wet environments, produces abundant seeds, and can form dense stands under favorable conditions. These characteristics could allow it to spread into sensitive habitats where it may compete with native vegetation, alter ecosystem processes, and reduce biodiversity in tropical island ecosystems. Because Hawaiʻi’s climate is suitable for many Australian wetland species, continued caution is warranted. Choosing a low risk or native alternative is recommended when such alternatives are available.

High Risk Traits:

• Can grow in regions with tropical and subtropical climates
  
• Other Melaleuca species are invasive
  
• May be unpalatable to animals
  
• Oils may be toxic or allergenic to people and animals
  
• Highly flammable; may increase fire risk in natural ecosystems and threaten structures
  
• Tolerates many soil types
  
• Forms dense thickets in native range
  
• Reproduces by seeds
  
• Hybridizes with other Melaleuca species
  
• Seeds dispersed by wind, probably water and intentionally by people
  
• Seeds capsules may remain on trees for two or three years, forming a persistent canopy seed bank
  
• Able to coppice and resprout after cutting; tolerates fire

Low Risk Traits:

• No reports of invasiveness or naturalization, but no evidence of widespread introduction outside native range
  
• Unarmed (no spines, thorns, or burrs)
  
• Valued source of essential oil
  
• May prefer high light environments (could limit spread into intact forests)
  
• Mostly self-incompatible (self-pollinated plants have low seed set)
  
• Not reported to spread vegetatively
  
• Herbicides may provide effective control