Family: Cupressaceae

Origin, Description & Uses:
Cryptomeria japonica, commonly known as Japanese cedar or sugi, is a tall evergreen conifer native to Japan, where it has long been valued for its straight trunk, fragrant reddish wood, and cultural significance. The tree has soft, needle-like leaves, fibrous reddish-brown bark, and a symmetrical, conical form that makes it attractive in landscapes. Outside its native range, Cryptomeria japonica is widely planted as an ornamental, windbreak, and timber tree. Its wood is lightweight, durable, and resistant to decay, making it popular for construction, fencing, and interior uses, as well as for forestry plantings.

Risks, Threats & Management:
In Hawaiʻi, Cryptomeria japonica is naturalized on Maui and Oʻahu, indicating its ability to reproduce and persist beyond cultivation. While it is not currently considered highly invasive, it does possess traits that are cause for concern, including adaptability to local conditions and the potential to spread from planted areas. If unmanaged, it could contribute to changes in forest structure or compete with native vegetation, particularly in cooler, wetter upland environments. Caution is recommended when planting or managing Japanese cedar in Hawaiʻi to ensure it does not negatively impact native ecosystems, and choosing native or clearly low-risk alternatives is encouraged where appropriate.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Grows in temperate to subtropical climates (may only grow at higher elevations in subtropical climates)
  
• Naturalized or naturalizing on West Maui (Hawaii), New Zealand, and possible the Azores
  
• May possess allelopathic properties
  
• Pollen may cause dermatitis or allergies in susceptible individuals
  
• Flammable and may increase fire risk
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Dense planted stands may limit recruitment or regeneration of desirable species
  
• Reproduces by seeds, and possibly by layering
  
• Self-compatible
  
• Seeds dispersed by wind and people (possibly rarely by birds)
  
• Seeds may persist in the soil for at least 1 year
  
• Able to coppice

Low Risk Traits:

• Despite widespread planting, few reports of naturalization, and no documentation of serious negative environmental impacts
  
• Unarmed (no spines, thorns or burrs)
  
• Valued as an ornamental and timber tree
  
• Vegetative spread by layering only in rare circumstances
  
• Reaches maturity in 5-10 years
  
• Herbicides may provide effective control