Boronia pinnata is a shrub reaching a height of 1.5 metres.
This attractive species occurs in most coastal areas of NSW (south to Nowra) extending into the central tablelands, as well as extending into southern Queensland.
Boronia spp. produce opposite leaves which can be simple or compound (sometimes on the same plant) and are usually aromatic (sometimes strongly-so). The leaves are compound and pinnate with 5-11 leaflets.
Boronia have complete flowers (bisexual and with all whorls present). The flowers are produced either solitarily or in groups, in the leaf axils, or, at the branch terminals. There are usually four sepals, four petals and generally eight stamens, surrounding one female part (carpel). Flowers are often pink to purple, which makes them easily identifiable in NSW bushland.
In this species, the flowers are carried in clusters held in the upper leaf axils. Each flower is about 1.5 centimetres in diameter, four-petalled and pale to deep pink in colour. A white-flowered form is also in cultivation. Flowers are both conspicuous, profuse and appear in spring. Both foliage and flowers are strongly aromatic.
Boronia pinnata is hardy, free flowering and prefers well drained soils in semi-shade.
It would an attractive and aromatic addition to native cottage gardens, rockeries and as a foreground plant in garden beds.
Plants appreciate light pruning after flowering. Best planted on a sandy free-draining soil.
Growing boronias can be a frustrating experience and they have a reputation for being difficult. Their attractiveness has led to substantial efforts to cultivate them. One tip is to try to grow forms that are local to your area, rather than attempting to grow those species from interstate. There are certainly some species that have proven easier to grow than others.
Most boronias have a short life span of two to three years in a garden situation but are a rewarding plant while healthy as they provide lovely fragrance and flowers in Spring.
For them to grow at their best, select a position with dappled sunlight and especially protection from hot afternoon sun in summer, as well as from wind, which they dislike.
The soil must be well drained and have an even supply of moisture. If they dry out, they will surely die.
Plating on a slight slope is said to work well.
For a longer life, the best way to grow them is in a medium sized pot, say 30 cm in diameter where drainage and moisture can be controlled. A sheltered patio or courtyard that receives at least a few hours sunlight a day would be ideal.
Fertilise after flowering.
The conventional wisdom is, think deeply about which species to plant and the location to plant it.
Propagate from cuttings.
Typically, boronias will die in a fire and regenerate form the seedbank.
Boronia is a genus of about 150 species in the citrus family Rutaceae. Most species are endemic to Australia and species can be found in all states. There are also 4 species in New Caledonia, which were previously placed in the genus Boronella. In 2020, several species of Boronia have been transferred to the genus Cyanothamnus (meaning “blue shrub or bush”), as these species have been found to be more closely related to other Rutaceae genera rather than other Boronia species. After the move of some species to Cyanothamnus, there are about 30 Boronia spp. in NSW.
Boronia – after Francesco Borone (1769-1794), an 18th century Italian botanist who assisted John Sibthorpe. Allegedly, he died at age 25, due to falling out a window whilst collecting plant specimens.
pinnata – Latin – referring to the obvious pinnate shape of the leaves (also meaning “finned”) – an arrangement where leaflets are arranged in opposite or 2-ranked pairs.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Boronia pinnata profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Boronia~pinnata
Australian Native Plants Society Australia – Boronia Family Profile Page
Gardening with Angus Website – Boronia for Beginners
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.