Cyanothamnus is a genus of flowering shrubs in the family Rutaceae (order Sapindales), native to Australia. The genus comprises around 23 accepted species of erect or spreading shrubs, typically bearing pinnate leaves arranged in opposite pairs — though a few species such as C. anemonifolius and C. nanus have simple leaves. The flowers appear singly or in cymes, with petals most often pink or white, occasionally blue or yellowish-green.
The genus was first described in 1839 by John Lindley in A Sketch of the Vegetation of the Swan River Colony, but for most of its subsequent history the constituent species were treated under the closely related genus Boronia. A molecular phylogenetic study published in 2020 demonstrated that Boronia as then circumscribed was polyphyletic, prompting the revival of Lindley's genus. A 2021 classification of the family Rutaceae places Cyanothamnus in the subfamily Zanthoxyloideae. Species are distributed across much of Australia, with representatives recorded from Western Australia, Queensland, New South Wales, Victoria, South Australia, and Tasmania.
Distribution
Cyanothamnus is endemic to Australia. Species are found across multiple states: Western Australia, Queensland, New South Wales, Victoria, South Australia, and Tasmania, with Western Australia having the highest concentration of endemic species.
Taxonomy Notes
Cyanothamnus was described by John Lindley in 1839 but was long lumped into Boronia. A 2020 molecular phylogenetic study showed Boronia sensu lato to be polyphyletic, leading to the reinstatement of Cyanothamnus. A 2021 family-level revision of Rutaceae places the genus in subfamily Zanthoxyloideae, order Sapindales.
