Family: Cactaceae

Cereus hildmannianus—commonly known as hedge cactus, queen of the night, Andes organ pipe, Peruvian apple, or spiny tree cactus—is a tall, columnar cactus native to South America, particularly regions of Argentina, Brazil, and Paraguay. It has thick, ribbed green stems with prominent spines and can grow into a tree-like form, often branching from the base or higher up the stem. Large, showy white flowers open at night and are followed by round, edible fruits sometimes referred to as “Peruvian apples.” Because of its dramatic form and drought tolerance, this species is widely planted as an ornamental, living fence, or landscape accent in dry and coastal areas. In Hawaiʻi, it is naturalized on Kauaʻi, Oʻahu, and Maui.

Despite its popularity in landscaping, Cereus hildmannianus poses ecological risks once it escapes cultivation. It can spread from discarded cuttings or fallen stem fragments, forming dense, spiny thickets that displace native plants and limit access for people and wildlife. Its sharp spines make infestations difficult and hazardous to manage, and dense growth can alter habitat structure in dry and coastal ecosystems. Where naturalized, this cactus may contribute to long-term changes in plant communities, highlighting the importance of careful planting, proper disposal of plant material, and choosing non-invasive alternatives when landscaping.

High Risk Traits:

• Climatically adaptable (tropical/subtropical)
  
• Environmental weed potential
  
• Naturalized beyond native range
  
• Spines, allelopathic, toxic to animals
  
• Host for pests
  
• Tolerates varied soils
  
• Viable seeds and natural hybridization
  
• Vegetative reproduction
  
• Human and bird dispersed
  
• Tolerates disturbance/fire

Low Risk Traits:

• Not parasitic, not toxic to humans
  
• No fire hazard or shade tolerance
  
• Not self-compatible
  
• Not dispersed by wind, water, or as a contaminant
  
• No prolific seed production or persistent seed bank
  
• No evidence of effective natural enemies