Cassinia is a genus of about fifty-two species of flowering plants in the daisy family, Asteraceae, native to Australia and New Zealand. Members of the genus are perennial shrubs — and occasionally small trees — typically reaching 0.5 to 2 metres in height, though a few species can grow to as much as 8 metres. The foliage is often viscid (sticky) and aromatic, and the plants tend to form dense, multistemmed crowns.
The leaves are simple and arranged alternately along the stems. They are usually narrow and linear, with margins that range from flat to strongly rolled under, ending in small pointed tips. This rolled-margin leaf form, combined with the often resinous coating, gives many species a characteristic fine, heath-like texture that helps them cope with the dry sclerophyll habitats they favour.
The flowers are the genus's most diagnostic feature. Tiny, bisexual florets — white, cream, yellow, or sometimes pinkish — are gathered into small heads (capitula), and the capitula in turn are arranged into showy cymose or paniculate inflorescences. Each head is enclosed by several rows of usually erect, boat-shaped involucral bracts that often contribute as much to the visual display as the florets themselves. The fruit is a small cylindrical cypsela bearing a pappus of short bristles, which aids wind dispersal.
The genus was formally described by Robert Brown in 1817 in Observations on the Natural Family of Plants called Compositae, and named in honour of the French botanist Alexandre de Cassini. Cassinia is most diverse across southeastern Australia, ranging from the Eyre Peninsula in South Australia through Victoria, Tasmania, New South Wales (including Lord Howe Island, where C. tenuifolia is endemic), and into southeastern Queensland; the genus also occurs in Western Australia and New Zealand. In dry sclerophyll woodland understoreys the shrubs can become locally dominant, particularly after disturbance, where their fast growth and dense habit make them important early colonisers. Well-known species include the common cassinia or dolly bush (C. aculeata), the drooping cassinia or Chinese scrub (C. arcuata), and the cough bush or dead finish (C. laevis).
Etymology
The genus Cassinia commemorates the French botanist Alexandre Henri Gabriel de Cassini (1781–1832), a specialist in the Asteraceae who described many of the family's tribes. Robert Brown applied the name when he formally established the genus in 1817.
Distribution
The genus is restricted to Australia and New Zealand. It reaches its greatest diversity in southeastern Australia, where species occur from South Australia's Eyre Peninsula east through Victoria and Tasmania, across the whole of New South Wales (including the offshore endemic C. tenuifolia on Lord Howe Island), and north into southeastern Queensland. Additional species are recorded from Western Australia and the Australian Capital Territory, and a smaller component of the genus extends to New Zealand. Sources differ slightly on the western and trans-Tasman extent: PlantNET NSW characterises Cassinia as restricted to southeastern Australia, while the Wikipedia genus article and Commons records explicitly include Western Australia and New Zealand.
Ecology
Most Cassinia species are multistemmed shrubs of dry sclerophyll woodland understoreys, where they can become locally dominant. They are well adapted to dry, open habitats and disturbed ground, and individual species span a wide altitudinal range — C. aculeata, for instance, grows from sea level to about 1,300 m and is often conspicuous in recently disturbed sites. Flowering typically peaks in the Southern Hemisphere summer (roughly November to February for C. aculeata), with the wind-dispersed cypselas helping the genus colonise gaps rapidly.
Cultivation
In horticulture Cassinia shrubs are valued as fast-growing, drought-tolerant evergreens. A typical cultivated Cassinia is an evergreen shrub reaching about 2 m × 2 m, hardy in USDA zones 8–11 and tolerating temperatures down to roughly -15 °C (though usually staying smaller in cooler climates). Plants prefer full sun and well-drained soil, adapt to sandy, loamy or clay substrates, and tolerate maritime exposure — qualities that make them particularly suited for use as a hedge in seaside gardens, with foliage that carries a honey-like scent. The common cassinia (C. aculeata) is similarly useful as a fast temporary screen, asking for moist well-drained soil and partial sun, but it is not salt-tolerant, can be short-lived without regular pruning, and its foliage may cause skin irritation in some people.
Propagation
Cassinia is propagated either from seed sown in spring under glass, or from half-ripe (semi-hardwood) cuttings taken in mid- to late summer and rooted in a propagation frame.
Cultural uses
The honey-scented foliage and long-lasting dried flowerheads of Cassinia species have given them a minor place in ornamental use. The leaves' honey-like scent and the shrubs' hedging habit suit them to seaside gardens, and the cut, dried inflorescences of C. aculeata are long-lasting in floral arrangements.
History
Cassinia was formally described by the Scottish botanist Robert Brown in 1817, in his Observations on the Natural Family of Plants called Compositae. Brown's treatment placed the new genus within the daisy family and dedicated it to Alexandre de Cassini. The name has been continuously accepted in subsequent global checklists, and the genus is recognised today by the GBIF Backbone Taxonomy as Cassinia R.Br., family Asteraceae.
Taxonomy notes
Cassinia R.Br. is placed in the family Asteraceae and currently encompasses roughly forty to fifty-two accepted species, depending on the treatment consulted: Wikipedia cites about fifty-two species, while the PlantNET NSW key gives approximately 40–45 species worldwide. GBIF lists the genus as an accepted name with the authority R.Br. Several species sit at the boundaries of the genus's range — C. tenuifolia, for example, is endemic to Lord Howe Island, and C. furtiva is known from only a single collection location — which has historically complicated regional keys.
