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A small shrub of about 1–2.5 metres in height by a similar width.
Boronia mollis grows in NSW, occurring naturally around Sydney, ranging as far north as Coffs Harbour, south to around Moss Vale, and inland as far as the Dividing Range, in open forest and woodlands on sandstone.
Boronia spp. produce opposite leaves which can be simple or compound (sometimes on the same plant) and are usually aromatic (sometimes strongly-so).
The foliage in this species is pinnate (compound leaves made up of a number of leaflets) with leaves to around 40 mm long. They are softly hairy when young but may become smooth on the upper surface as they mature. The hairy foliage is one of the features that distinguishes B. mollis from the closely related B. fraseri. The foliage has a very strong smell.
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.
The flowers of this species are pink. They are about 10–15 mm in diameter, well displayed in clusters from the upper leaf axils. Flowering occurs from mid winter to mid spring.
The fruit of Boronia are described as a schizocarp-capsule; a capsule that splits into even segments, which each segment called a coccus. The fruit are 4 to 5 mm long and 2.5 to 3 mm wide.
This is a very popular species in cultivation and is hardier than many other boronias in the garden although difficult to maintain for long periods.
It requires a well-drained moist soil, preferably in semi shade although full sun is tolerated. It seems to be reasonably tolerant of dry conditions once established and is tolerant of at least moderate frost. It is best to mulch plants to provide a cool root run. The foliage has a very strong smell; in the Editor’s opinion – smelling similarly to a dirty BBQ hot-plate!
Boronias are subject to root rot and thus a well-drained soil without excess watering is needed to prevent this.
The cultivar ‘Lorne Pride’ is especially good and forms a rounded shrub to about 1 metre in height.
Propagation from seed is difficult but cuttings usually strike readily from current season’s growth.
Boronias will typically 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.
mollis…. Latin meaning “soft”, referring to the foliage.
Although somewhat rare in the wild, it is not considered to be at risk of extinction.
Australian Native Plants Society Australia – Boronia Family Profile Page
https://anpsa.org.au/genera/boronia-family/
NSW Flora Online (PlantNET) – Boronia mollis profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Boronia~mollis
Australian National Herbarium – Boronia mollis profile page https://www.anbg.gov.au/gnp/gnp6/bor-moll.html
Wikipedia – Boronia mollis profile page https://en.wikipedia.org/wiki/Boronia_mollis
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.