Family: Corynocarpaceae

Karaka nut (Corynocarpus laevigatus) is a large, evergreen tree native to New Zealand and traditionally valued by Māori for its nutritious seeds after careful processing. The tree has broad, glossy green leaves and produces bright orange, fleshy fruits that make it attractive as an ornamental and shade tree. Because of its dense canopy and tolerance of a range of conditions, karaka nut was historically planted in Hawaiʻi for forestry, erosion control, and landscape use. It was introduced to Kauaʻi prior to 1891 and was already noted as naturalized in the Kōkeʻe region by 1912.

In Hawaiʻi, karaka nut is now naturalized primarily on Kauaʻi, with additional populations on Oʻahu, Molokaʻi, and Hawaiʻi Island. Its spread was greatly accelerated in 1929, when seeds were broadcast by airplane over the interior of Kauaʻi, leading to widespread establishment. Karaka nut forms dense stands and heavy shade that exclude native plants and reduce forest diversity, posing a significant threat to native ecosystems. Once established, it can be difficult to control due to its size, longevity, and prolific regeneration. Because of these impacts, karaka nut is considered a high-risk species in Hawaiʻi, and choosing native or low-risk alternatives is strongly recommended to help protect local forests and biodiversity.

High Risk Traits:

• Naturalized beyond native range (Hawaii)
  
• Environmental weed – forms monotypic stands
  
• Broad climate suitability
  
• Tolerates a range of soil types
  
• Forms dense thickets
  
• Produces viable, bird- and pig-dispersed seeds
  
• Self-compatible (gynodioecious)
  
• Seeds survive gut passage
  
• Intentionally planted by humans
  
• History of repeated introductions
  
• Lacks effective natural enemies in invaded areas

Low Risk Traits:

• Not an agricultural or garden weed
  
• No spines/thorns
  
• Not toxic to animals when ripe
  
• Not a major pest/disease host
  
• Fire-retardant
  
• No vegetative reproduction
  
• Slow to mature (~5 years)
  
• Low unintentional dispersal (large seeds)
  
• Low seed density per m²
  
• Controllable with herbicides