Family: Onagraceae

Origin, Description & Uses:
Epilobium billardiereanum, commonly known as Aboriginal willowherb or smooth willowherb, is a small herbaceous plant native to Australia and New Zealand. It typically grows as a slender annual or short-lived perennial with narrow leaves and small pale pink to whitish flowers. Like many willowherbs, it produces numerous tiny seeds equipped with silky hairs that allow them to be carried long distances by wind. This species is sometimes found in disturbed habitats such as roadsides, gardens, pastures, and open fields. Although it has no major ornamental or agricultural use, it can occasionally appear as a volunteer plant in cultivated or landscaped areas.

Risks & Threats:
In Hawaiʻi, Aboriginal willowherb is naturalized on Kauaʻi, Oʻahu, Maui, and Hawaiʻi Island. It reproduces readily by producing large numbers of wind-dispersed seeds and can quickly colonize disturbed soils and open habitats. These traits are cause for concern because they allow the plant to spread easily and potentially compete with native vegetation. As a result, this species could detrimentally impact tropical island ecosystems by establishing in natural areas and altering plant communities. Because of these risks, it is recommended to avoid planting or intentionally spreading this species and instead choose low-risk or native plant alternatives better suited for Hawaiʻi’s landscapes.

High Risk Traits:

• Elevation range exceeds 2000 m, demonstrating environmental versatility
  
• Temperate species that is naturalized in tropical climates
  
• Naturalized on Kauai, Oahu, Maui and Hawaii islands
  
• Environmental weed that threatens the endangered Hawaiian fern Diplazium molokaiense
  
• Other Epilobium species are invasive
  
• Reproduces by seeds and vegetatively
  
• Able to reach maturity in one growing season
  
• Seeds dispersed by wind and possibly due to human activities
  
• Able to resprout after fires

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Palatable go grazing animals
  
• Non-toxic
  
• May not be able to establish in dense shade
  
• Certain herbicides may provide effective control