Family: Fabaceae

Acacia mearnsii, commonly known as black wattle, is a fast-growing, nitrogen-fixing tree native to southeastern Australia. It is widely cultivated around the world for its tannin-rich bark, which is used in leather production, as well as for timber, fuelwood, and erosion control. The species is recognizable by its feathery, bright green phyllodes (leaf-like structures) and clusters of creamy-yellow, fragrant flowers that bloom in late winter to spring. Black wattle thrives in a variety of soils and climates, particularly in disturbed or degraded areas, which contributes to its popularity in forestry and land restoration projects.

Despite its economic value, black wattle is highly invasive in many regions outside its native range, including parts of Africa, South America, and the Pacific Islands. It forms dense stands that outcompete native vegetation, alter soil chemistry through nitrogen enrichment, and reduce biodiversity. Its prolific seed production and ability to sprout from stumps make it difficult to control once established. Because of these traits, Acacia mearnsii is often considered a high-risk species for naturalization and ecological disruption in non-native areas.

High Risk Traits:

• Naturalized in multiple regions (e.g., southern Africa, Hawaii).
  
• Forms dense thickets, displacing native vegetation.
  
• Classified as an environmental and agricultural weed.
  
• Unpalatable to livestock due to high tannin content.
  
• Fast-growing nitrogen-fixing tree (up to 3 m/year).
  
• Produces abundant, long-lived seeds (viable for years).
  
• Self-compatible with partial outcrossing.
  
• Tolerates a wide range of soils, including poor, eroded, and volcanic soils.
  
• Thrives in disturbed areas and resprouts vigorously after fire or cutting.
  
• Seeds spread by water, birds, and human activities.
  
• Forms persistent seed banks in soil.
  
• Increases wildfire risk due to dense growth and dry biomass.
  
• Benefits from fire (resprouting and seed germination).

Low Risk Traits:

• Not Shade-Tolerant
  
• Non-Toxic
  
• No Vegetative Spread