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Boronia microphylla

Small-leaved Boronia

Family: Rutaceae

A shrub to 1 metre with with young branches covered in small, warty glands and scattered bristly hairs.

It has a large range over NSW, with disjunct occurrences; northwards from around the west of Kempsey, growing on the Northern Tablelands and western North Coast, extending into Queensland; then south from around Mudgee and Kandos (with some occurrences near Orange), through Lithgow and down to the Southern Highlands in disjunct patches. It can then be found from west of Milton to the west of Narooma.

It grows in heath and dry sclerophyll woodland and forest 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).
In this species, leaves are compound-pinnate with 5 to 15 leaflets, with overall leaf length about 30 mm long, leaflets are spathulate to cuneate (wedge-shaped) to about 1 cm long and 0.4 cm wide, with the terminal leaflet usually shorter than the rest, and with the central part of the leaf winged.

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 arranged in groups in the upper leaf axils in up to groups of 5, bright pink to rose-purple, occurring from October to February.

The fruit of Boronia are described as a schizocarp-capsule; a capsule that splits into even segments, which each segment called a coccus.

In this species, the cocci are hairless and less than 5 mm long.

B. microphylla has been in cultivation for many years and is a very desirable garden plant. Although it has proven to be easier to maintain than many other members of the genus, it cannot be regarded as an easy plant for the non-enthusiast. It is not a common plant to source at a nursery so enquire at your local native nurseries.

In the garden

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.

Propagation

Boronias can be propagated from cutting but overall you will have limited success with most but not all species.

Other information

Boronia is a genus of about 160 species of flowering plants in the citrus family Rutaceae. Most species are endemic to Australia and species can be found in all states. There are also some species in New Caledonia, which were previously placed in the genus Boronella.

Boronias are likely killed in fires and regenerate from the seed bank.

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.
microphylla – from Greek micro (μικρό) meaning “small” and phyllo (φύλλο) meaning “leaf”, referring to the comparitivley small leaf size of this plant and, hence, its common name.

Not considered to be at risk with extinction in the wild.

Australian Native Plants Society Australia – Boronia Profile Page
http://anpsa.org.au/boronia9.html

Wikipedia Boronia and Boronia microphylla Profile Pages
https://en.wikipedia.org/wiki/Boronia
https://en.wikipedia.org/wiki/Boronia_microphylla

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.

NSW Flora Online (PlantNET) – Boronia microphylla Profile Page
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Boronia~microphylla

By Jeff Howes, edited Dan Clarke