Family: Rosaceae

Origin, Description & Uses
Sorbus aucuparia (European mountain ash or rowan) is native to a wide region spanning Europe to Iran and from the Russian Far East through northern China and Korea. It is a deciduous, small to medium-sized tree valued for its attractive, finely divided compound leaves, clusters of white spring flowers, and bright red-orange berry-like fruits that persist into fall. Widely planted as an ornamental in temperate regions, it is also appreciated for its wildlife value, as the fruits are eaten by birds and other animals. In parts of its native range, the fruits have been used for making jellies, preserves, and traditional remedies, and the tree is sometimes planted in landscapes for its seasonal color and hardiness.

Risks & Threats
Although Sorbus aucuparia is currently not known to be naturalized in the Hawaiian Islands, it possesses several traits that raise concern for potential ecological impacts if it were to establish. It produces abundant, bird-dispersed fruits that can facilitate long-distance spread, and it is adaptable across a range of environmental conditions, including disturbed habitats. In other regions outside its native range, it has shown the ability to escape cultivation and persist in natural areas, raising concerns about potential invasiveness in suitable climates, particularly at higher elevations or cooler microclimates in tropical islands. If introduced, it could compete with native vegetation and alter habitat structure over time. Given these risks, it is recommended to choose low-risk or Hawaii-native alternatives whenever suitable options are available for landscaping and restoration.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Naturalized in Canada, New Zealand, Patagonia, Alaska and possibly elsewhere
  
• Controlled as an environmental weed in Alaska
  
• Other Sorbus species are invasive
  
• Host for pests and pathogens of Rosaceae
  
• Seeds may be toxic
  
• Tolerates many soil types
  
• Seedlings and sapling are Shade-tolerant
  
• Capable for forming pure stands
  
• Reproduces by seeds
  
• Hybridizes with other Sorbus species
  
• Seeds dispersed by birds, mammals, water and intentionally by people
  
• Seeds may persist in soil for 5 years
  
• Able to coppice and resprout after cutting

Low Risk Traits:

• From cooler, temperate climates. May only be invasive at higher elevations of tropical environments
  
• Unarmed (no spines, thorns, or burrs)
  
• Palatable to browsing animals
  
• Ornamental
  
• Self-incompatible
  
• Vegetative spread may be limited to a few suckers
  
• Reaches maturity in 10+ years