Family: Pinaceae

Origin, Description & Uses
Pinus radiata, commonly known as Monterey pine, is native to a small area of coastal California and two islands off the coast of Mexico, including Guadalupe and Cedros Islands. This fast-growing evergreen conifer is recognized for its tall straight trunk, dense rounded crown, and clusters of bright green needles. Monterey pine is one of the world’s most widely planted timber trees and has been used extensively for lumber, paper production, windbreaks, erosion control, and ornamental landscaping. In Hawaiʻi, it has been planted in cooler upland areas, including parts of Maui, where it has become naturalized.

Risks & Threats
Monterey pine is naturalized in Hawaiʻi and possesses traits that are cause for concern in tropical island ecosystems. This species grows rapidly, produces abundant seeds, and can spread beyond cultivation into nearby natural areas. Dense stands may shade out native vegetation, alter soil conditions through heavy needle litter, and increase fire risk by creating large accumulations of flammable material. In sensitive Hawaiian ecosystems, these changes can reduce biodiversity and interfere with native forest regeneration. Because of its invasive potential and ability to negatively impact island habitats, Monterey pine is considered a high-risk species in Hawaiʻi. Plant Pono recommends choosing low-risk or native alternatives whenever possible.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Widely naturalized
  
• An environmental weed in Australia, South Africa and Hawaii
  
• Other Pinus species have become invasive
  
• Exposure to pollen or sawdust may cause allergies or dermatitis
  
• Increases fire risk
  
• Seedling and saplings are Shade-tolerant
  
• Tolerates many soil types
  
• Able to form dense stands
  
• Reproduces by seeds
  
• Able to hybridize with other Pinus species
  
• Self-compatible
  
• Seeds dispersed by wind, rarely by birds and intentionally by people
  
• Serotinous cones “store” seeds for years until exposed to fire or high temperatures
  
• Older trees tolerate ground fires, pole-stage trees tolerate low intensity fires

Low Risk Traits:

• Valuable commercial tree (pulp, timber, Christmas trees, landscaping)
  
• Unarmed (no spines, thorns or burrs)
  
• Palatable to a number of browsing animals
  
• Not reported to spread vegetatively
  
• Reaches maturity in 5+ years
  
• Herbicides may provide effective control