Family: Malvaceae

Brachychiton rupestris, commonly known as the narrow-leaf bottletree or Queensland bottletree, is a distinctive tree native to Queensland, Australia. It’s easily recognized by its swollen, bottle-shaped trunk that stores water—an adaptation to drought-prone environments. The tree has narrow, glossy leaves and produces small, creamy-yellow flowers followed by woody pods. Bottletrees are widely planted as ornamental shade trees in warm climates because of their drought tolerance, unique shape, and low maintenance needs. They’re especially valued in landscaping for adding character and visual interest.

Although Brachychiton rupestris is not currently known to be naturalized in Hawaiʻi, it does possess certain traits—such as drought tolerance, adaptability to varied soils, and seed production—that raise some concern about its potential to establish in the future. At this time, there is no evidence that it is invasive or that it threatens native ecosystems, but its characteristics suggest it should be monitored carefully. Further evaluation is needed to determine whether this species could impact Hawai‘i’s natural areas if planted more widely.

High Risk Traits:

• Broad climate suitability
  
• Thrives in tropical climates
  
• Other Brachychiton species have become invasive
  
• Nitrate poisoning may occur if fed to cattle
  
• Seeds surrounded by irritant hairs
  
• Moderate flammability; may increase fire risk in fire prone areas
  
• Tolerates many soil types
  
• Reproduces by seed
  
• Hybridizes with other Brachychiton species
  
• Seeds dispersed intentionally by people and possibly by bird and rodent seed predators
  
• Able to sucker and resprout after fire and probably cutting
  
• Limited ecological information (esp. reproductive biology) reduces accuracy of risk prediction

Low Risk Traits:

• No reports of invasiveness or naturalization
  
• Unarmed (no spines, thorns, or burrs)
  
• Provides fodder for livestock (palatable despite potential nitrate toxicity)
  
• Ornamental
  
• Not reported to spread vegetatively
  
• Slow growth rate
  
• Relatively large seeds unlikely to be accidentally dispersed