Family: Anacardiaceae

Origin, Description & Uses
Searsia lancea, commonly known as willow rhus, is a medium-sized evergreen tree native to southern Africa, ranging from Zambia to South Africa. It is valued for its graceful, weeping form, narrow willow-like leaves, and tolerance of drought, heat, and poor soils. The tree is widely planted as an ornamental shade tree in parks, gardens, and streetscapes, particularly in dry climates. It also provides habitat and food resources for wildlife within its native range and is appreciated for its attractive appearance and low maintenance requirements.

Risks & Threats
Although Searsia lancea is not currently known to be naturalized in the Hawaiian Islands, it possesses several traits that raise concerns for tropical island ecosystems. The species produces abundant fruits that can be dispersed by birds and other animals, potentially allowing it to spread beyond cultivation. Its adaptability to a wide range of environmental conditions, drought tolerance, and ability to establish in disturbed habitats increase its potential to persist and spread if introduced into suitable areas. Because of these characteristics, the species has been assessed as High Risk. If it were to escape cultivation, it could compete with native vegetation and alter natural ecosystems. As a precaution, choosing a low-risk or native alternative is recommended whenever suitable alternatives are available.

High Risk Traits:

• Naturalized and invasive in the southwestern U.S.
  
• Invades desert washes and riparian areas, altering hydrology and increasing erosion.
  
• Forms dense canopies that shade out and displace native species.
  
• Produces abundant seeds dispersed by birds and floodwater; spreads ~0.5 mi/year.
  
• Resprouts vigorously from roots and stumps after cutting or fire.
  
• Pollen is highly allergenic to humans.
  
• Suspected allelopathic (inhibits nearby plants).
  
• Contains volatile oils, increasing fire risk.
  
• Widely planted as an ornamental, aiding spread.
  
• Dispersed intentionally by people, by birds, and by water.

Low Risk Traits:

• Palatable and non-toxic to livestock and wildlife.
  
• Lacks spines, thorns, or burrs.
  
• Does not reproduce by fragmentation.
  
• Dioecious (requires cross-pollination).
  
• Not wind-dispersed.
  
• Not a known produce contaminant.
  
• Not highly prolific (does not exceed 1,000 seeds/m²).