Family: Rhamnaceae

Origin, Description & Uses:
Frangula alnus is a small to medium deciduous tree native to Europe, northern Africa, and parts of Asia. It typically grows 3–6 meters tall, with smooth, dark bark and glossy green leaves that turn yellow in autumn. This species produces small, greenish-white flowers followed by dark purple to black berries. Alder buckthorn has been used historically for medicinal purposes, dyes, and as an ornamental plant in gardens and landscaping. Its fast growth and adaptability to different soils make it a popular choice for hedges and erosion control in some regions.

Risks & Threats:
Although Frangula alnus is not currently known to be naturalized in the Hawaiian Islands, it is considered a high-risk species due to its aggressive growth, ability to spread rapidly, and potential to outcompete native plants. In other regions, it has become invasive, forming dense thickets that disrupt native ecosystems and reduce biodiversity. Because of these traits, introducing this species could negatively impact Hawaii’s tropical island ecosystems. It is recommended to choose a low-risk or native alternative for landscaping or restoration projects.

High Risk Traits:

• Broad climate suitability (in temperate climates)
  
• Widely naturalized in North America
  
• An environmental weed that reduces native species richness
  
• Toxic to animals and accidental poisoning of people is possible
  
• Tolerates many soil types
  
• Forms dense stands
  
• Seeds dispersed by birds and other frugivorous animals
  
• Reaches maturity in 2 years
  
• Seeds may persist in soil for 2 or more years
  
• Able to coppice and resprout after cutting

Low Risk Traits:

• Grows in temperate climates and may only be a threat to higher elevation in tropical islands
  
• Unarmed (no spines, thorns or burrs)
  
• Palatable to deer and other browsing animals (although toxic)
  
• Relatively Shade-intolerant
  
• Mostly self-incompatible (but not 100%)
  
• Not reported to spread vegetatively (but able to sucker or coppice prolifically if cut)
  
• Herbicides may provide effective control