Family: Fagaceae

Origin, Description & Uses
Quercus suber (cork oak) is native to the western and central Mediterranean region, where it grows in warm, dry climates. It is a long-lived evergreen oak known for its thick, spongy bark, which is harvested as cork without harming the tree. Cork oak is widely valued for commercial cork production used in wine bottle stoppers, flooring, insulation, and other specialty products. It is also planted as an ornamental and shade tree in parks and large landscapes due to its attractive form, dense canopy, and drought tolerance once established.

Risks & Threats
In Hawaiʻi, cork oak is now naturalized, meaning it is reproducing outside of cultivation. While it has not yet been widely documented as highly invasive, it does possess traits that are cause for concern, including long lifespan, heavy acorn production, and the ability to establish in a range of conditions. These characteristics could allow it to spread and potentially compete with native vegetation over time, especially in suitable upland habitats. Its ecological impacts in Hawaiʻi are still not fully understood, so ongoing evaluation is needed. Caution is recommended to ensure it will not negatively impact Hawaii’s ecosystems, and careful monitoring should continue to assess any signs of spread or ecosystem disruption.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Naturalized in Australia and Hawai'i Island
  
• Other Quercus species have become invasive
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Forms dense stands in native range
  
• Reproduces by seeds and root suckers
  
• Hybridizes with other Quercus species
  
• Seeds dispersed by seed hoarding birds, rodents and intentionally by people
  
• Potential for prolific seed production (mast seeder), but densities unspecified
  
• Able to coppice

Low Risk Traits:

• No reports of detrimental impacts where naturalized
  
• Unarmed (no spines, thorns, or burrs)
  
• Palatable to browsing animals
  
• Non-toxic
  
• Ornamental
  
• Self-incompatible
  
• Reaches maturity in 10-12 years
  
• Recalcitrant seeds