Family: Asteraceae
Cassinia arcuata, commonly known as biddybush, Chinese shrub, drooping cassinia, siftingbush, or siftonbush, is a shrub to small tree native to Australia. It typically grows 6–20 feet tall and is easily recognized by its narrow, gray-green leaves and clusters of small, creamy white flowers that give off a noticeable scent. The foliage has a soft, felted texture, and the plant often has a drooping or airy appearance. Cassinia arcuata has been planted outside its native range for ornamental use, as a windbreak, and occasionally for erosion control because it tolerates poor soils and dry conditions.
Despite its usefulness, Cassinia arcuata can pose ecological risks where it is introduced. It produces large numbers of lightweight seeds that are easily spread by wind, allowing it to establish quickly and form dense stands. In suitable climates, this can lead to displacement of native vegetation and reduced habitat quality. Its ability to thrive in disturbed areas makes it particularly concerning near natural landscapes. Because of this invasive potential, it is not recommended for planting in Hawaiʻi.
High Risk Traits:
- Naturalized where grown
- Broad climate and soil adaptability
- Repeated introductions outside native range
- Weed in agricultural, environmental, and disturbed areas
- Allelopathic, toxic to animals and humans, unpalatable
- Increases fire risk, shade tolerant, forms thickets
- Produces viable seed, self-compatible, hybridizes, spreads vegetatively
- Wind-dispersed and human-mediated dispersal
- High seed production, tolerates damage and control measures
Low Risk Traits:
- Not spiny, parasitic
- No water, bird, or external animal dispersal
- No long-term seed bank
