Family: Simaroubaceae

An invasive tree that spreads from initial plantings.

Native to central China and Taiwan, tree of heaven grows in a wide variety of climates and soil types. Advertised as a ‘fast-growing, exotic tree,’ it was imported to the mainland USA in the late 1700s. Today, it is considered invasive in over 30 states. One specimen was found in cultivation in Kaua’i, which was promptly eradicated. To date, no more trees are known to be present anywhere in the state.

Description and Dispersal:

• A tall tree up to 80 ft with smooth stems and pale gray bark
  
• 10-41 small leaflets form large compound leaves (1-4 ft long), each leaflet has one or more teeth along its edge
  
• Small, pale yellow to greenish flowers grow in clusters on the tip of the branches; reddish-orange fruit is flat and twisted growing in large bunches up to 12 in across
  
• Spread by seeds and suckers, seeds are dispersed by wind, water, and birds

High Risk Traits:

• Highly Invasive: Naturalized on every continent except Antarctica.
  
• Significant Environmental Impact: Outcompetes natives, alters soil chemistry, and forms dense, allelopathic thickets.
  
• Extreme Versatility: Tolerates a wide range of climates, soils, drought, and shade.
  
• Prolific Reproduction: Produces hundreds of thousands of wind and water-dispersed seeds.
  
• Rapid Growth & Early Maturity: Can flower within weeks of germination.
  
• Aggressive Vegetative Spread: Reproduces readily from root fragments and suckers, especially after damage.
  
• Disturbance-Adapted: Thrives after fire, cutting, or other landscape disturbances.
  
• Intentionally Planted: Widely cultivated as an ornamental, facilitating its spread.

Low Risk Traits:

• Absent from Hawaii: Not currently established there, preventing natural spread.
  
• Unpalatable to Wildlife: Avoided by many grazers and seed predators.
  
• Dioecious: Requires separate male and female plants to set seed (though clonal spread mitigates this).
  
• Short-Lived Seed Bank: Seeds lack long-term persistence in the soil.
  
• Not a Major Pest Host: Generally resistant to pests and diseases in its introduced range.