Family: Cupressaceae

Origin, Description & Uses
Hesperocyparis arizonica, commonly known as Arizona cypress, is native to the southwestern United States and northern Mexico. This evergreen conifer is valued for its attractive blue-green to silvery foliage, conical form, and aromatic wood. It can grow 30–50 feet tall and is well adapted to dry climates, tolerating heat, drought, and poor soils. Arizona cypress is widely planted as an ornamental tree, windbreak, or privacy screen, and is sometimes used in reforestation and erosion control projects in arid regions.

Risks & Threats
Although Hesperocyparis arizonica is not currently known to be naturalized in the Hawaiian Islands, it possesses traits that raise concern for tropical island ecosystems. It produces abundant seeds, tolerates a range of environmental conditions, and can establish in disturbed areas—characteristics often associated with invasive potential. In similar climates elsewhere, it has shown the ability to spread beyond cultivation. If it were to escape into sensitive habitats in Hawaiʻi, it could compete with native plants, alter fire regimes, and change ecosystem structure. For these reasons, Plant Pono recommends choosing a low-risk or native alternative better suited to supporting Hawaiʻi’s unique environments.

High Risk Traits:

• Naturalized in Australia
  
• Environmental weed in Hawaii (impacts native species/habitat)
  
• Congeneric weeds
  
• Broad climate tolerance (0–2400 m elevation)
  
• Repeated, large-scale introductions worldwide
  
• Allelopathic (acidic litter suppresses other plants)
  
• Pollen causes human allergies
  
• Host for serious pest (Cinara cuppressi)
  
• Wide soil tolerance (sand, loam, acidic, alkaline)
  
• Wind-dispersed seeds
  
• Intentional & unintentional dispersal (plantings, machinery)
  
• Persistent seed bank (serotinous cones, seeds viable years)
  
• Fire-adapted (benefits from fire)

Low Risk Traits:

• Not an agricultural/horticultural weed
  
• Non-toxic to animals
  
• Shade intolerant (requires full sun)
  
• No vegetative spread
  
• No bird/animal dispersal (not adapted for gut or external transport)
  
• Long generation time (>4 years for significant seed production)