Family: Fabaceae
Acacia angustissima (fern acacia) is a tropical shrub or small tree native to the Americas, but it has been introduced to various regions worldwide, including Australia, Southeast Asia, and Africa. This species is classified as a high-risk invasive plant due to its ability to form dense thickets, prolific seed production, and long-lived seed bank. It thrives in tropical and subtropical climates, tolerates a wide range of soil conditions, and can regenerate rapidly after disturbances such as fire or cutting. Its nitrogen-fixing ability and rapid growth allow it to outcompete native vegetation, particularly in disturbed areas like roadsides and rangelands. Additionally, its seeds are dispersed by animals and water, further facilitating its spread.
Despite its potential as a fodder plant, Acacia angustissima poses significant ecological risks. It has low palatability for livestock and contains anti-nutritive compounds, limiting its agricultural value. The plant’s invasive traits—such as vegetative reproduction, environmental adaptability, and resistance to herbicides—make it difficult to control once established. Given its history of naturalization and potential to disrupt ecosystems, caution is advised when introducing this species to new regions. Preventative measures and early detection are critical to mitigating its impact on native habitats and biodiversity.
High Risk Traits:
- Tolerates a wide range of climates, and elevation range exceeds 2000 m, demonstrating environmental versatility
- Thrives in tropical climates
- Naturalized in Australia, Papua New Guinea and perhaps elsewhere
- Identified as a potentially weedy species, with warnings that Extreme caution should be exercised in introducing it to exotic environments
- Potentially toxic to grazing animals
- Tolerates many soil types
- Capable of forming dense thickets
- N-fixing (may alter soil chemistry)
- Reproduces by seeds and vegetatively by rhizomes
- Rapid growth rate
- Seeds dispersed by animals that consume them (e.g. cattle or birds) or by water movement
- Prolific seed production
- Seeds form a persistent seed bank (5+ years)
- Able to coppice and resprout after cutting and tolerates fire
Low Risk Traits:
- Unarmed (no spines or thorns)
- Provides fodder for livestock (palatable despite reports of toxicity)
- Reported to be self-incompatible
