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Boronia crenulata, sometimes known as the Aniseed Boronia, is a Western Australian native and is found in the southwest corner of that state.
This small shrub will reach a height of about 1 metre with a similar spread.
Boronia spp. produce opposite leaves which can be simple or compound (sometimes on the same plant) and are usually aromatic (sometimes strongly-so). This species has simple leaves which are spoon-shaped, about 1.5 centimetres long with a strong aniseed aroma (hence the common name).
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.
This species has delicate, pink flowers that are present for most of the year with the heaviest blooming from late winter to spring. Some plants may sucker.
The fruit of Boronia are described as a schizocarp-capsule; a capsule that splits into even segments, which each segment called a coccus. Dimensions of this species are unknown.
Authors note: When purchased this plant, it was labelled ‘Pink Passion’. We don’t know how this cultivar differs from the species probably by not very much.Previously, boronias have not featured in our cold climate garden. We felt that perhaps they were too delicate for our exposed situation. Also we had little or no success in propagation. B. crenulata has changed our opinion on both counts. This species seems very hardy and cutting propagation has proved to be rather successful. In less than 12 months we have recently potted on the second batch of struck cuttings giving a total of 13 plants rather than one. Perhaps it is time to try other boronias both in our cold climate garden and propagating bench.
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.
Planting 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, as above, from cuttings.
Boronia crenulata was first named from collections made in the early 1800’s from material collected at King Georges Sound, Western Australia.
Typically, boronias will die in a fire and regenerate from the seed bank.
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.
crenulata – Latin – meaning “crenulate” – where the edge of something has really fine rounded teeth or segments – referring to the leaf margins.
This species is not known to be at risk of extinction in the wild.
Government of Western Australia – Botanic Gardens and Parks Authority – Boronia crenulata profile page https://www.bgpa.wa.gov.au/about-us/horticulture/plant-of-the-month/1827…
Gardening with Angus – Boronia crenulata profile page https://www.gardeningwithangus.com.au/boronia-crenulata-aniseed-boronia/
Australian Native Plants Society Australia – Boronia Family Profile Page
https://anpsa.org.au/genera/boronia-family/
Gardening with Angus Website – Boronia for Beginners
https://www.gardeningwithangus.com.au/boronias-for-beginners-2/
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.