Family: Fabaceae

Origin, Description & Uses
Parkinsonia aculeata, commonly known as Jerusalem thorn, is a thorny small tree or large shrub native to Mexico, the Caribbean, and parts of Central and South America extending to northern Argentina. It is recognized for its airy green branches, feathery foliage, sharp spines, and bright yellow flowers that bloom over much of the year. The species is drought tolerant and adaptable to hot, dry climates, making it popular as an ornamental tree, hedge plant, shade tree, and barrier planting in tropical and subtropical regions. It has also been used for erosion control and occasionally as a source of firewood or livestock shelter. In Hawai‘i, this species has become naturalized on Kaua‘i, O‘ahu, and Maui.

Risks & Threats
Jerusalem thorn is considered a high risk species because it possesses traits associated with invasive behavior in tropical environments. It grows rapidly, produces abundant long-lived seeds, and forms dense thorny thickets that can outcompete native vegetation and restrict access for people and wildlife. The species is capable of spreading along roadsides, dry forests, pastures, waterways, and disturbed habitats, where it may alter ecosystem structure and reduce biodiversity. Its sharp spines can also create hazards for livestock and recreation. Because this species is naturalized in Hawai‘i and could detrimentally impact tropical island ecosystems, caution is strongly advised. When possible, choosing a low risk or native alternative is recommended to help protect Hawai‘i’s unique environments.

High Risk Traits:

• Naturalized & weedy outside native range (Kaua'i, Maui, O'ahu, Australia, Africa)
  
• Agricultural and environmental weed (blocks waterways, threatens bird habitats)
  
• Produces spines/thorns
  
• Forms dense thickets
  
• Creates fire hazard (accumulates leaf litter)
  
• Tolerates wide range of soil conditions
  
• Reproduces by viable seed
  
• Hybridizes naturally
  
• Fast growth, reaching maturity in ~2 years
  
• Seeds dispersed by water, birds, animals, and human activity
  
• Seeds survive gut passage
  
• Persistent seed bank (>1 year)
  
• Tolerates pruning/coppicing (responds well to mutilation)

Low Risk Traits:

• No evidence of toxicity to animals or humans
  
• Not shade tolerant
  
• No vegetative fragmentation
  
• No wind-adapted propagules
  
• Well controlled by herbicides