fbpx

Boronia polygalifolia

Dwarf Boronia, Milkwort-leaved Boronia or Milkwort Boronia

Family: Rutaceae

A low-lying spreading shrub to almost a herb, growing to 0.6 metres tall but usually smaller and ground-hugging, with stems up to 0.3 metres long.

It has a large natural spread in NSW, growing from Coolum Beach in Queensland, south into NSW along the coast and tablelands, down to just south of Tuross Head, with disjunct records at Tathra and Geehi. There are also records in Victoria.
(This editor recalls seeing plants in urban bushland reserves in East Hills in Sydney back in 2006).

It is found in open dry sclerophyll woodland and forest, as well as heath in rocky outcrops.

The stems are hairless.

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 simple (uni-foliolate) linear to elliptic, to 30 mm long and to 6 mm wide with the edges recurved or rolled under.

Boronia spp. 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, flowers are usually produced singularly, but sometimes up to three in the leaf axils, pale to bright pink, occurring from September to January.

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, it is a smooth capsule to 5 mm long.

In the garden

Not much is currently known about the cultivation of this species, and it is a very small plant which might not be preferred for a garden. It may be able to be grown well if plants could be sourced. It may be cultivated more commonly in the future. There is some information available in the references that is can be grown in moist soils.

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

Note: this species has, in 2013, being renamed Cyanothamnus polygalifolius. However, it is unclear at the time of writing, whether it will retain this name based on a later publication in 2020. This profile may be updated with this name in the future.

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 will likely die in a fire 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.
polygalifolia – Latin – having leaves similar to plants in the genus Polygala – a genus for which both native and weed-species exist in Australia.

This species is not considered to be at risk of extinction in the wild.

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

Wikipedia – Boronia and Cyanothamnus polygalifolius Profile Pages
https://en.wikipedia.org/wiki/Boronia
https://en.wikipedia.org/wiki/Cyanothamnus_polygalifolius

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 polygalifolia Profile Page
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Boronia~polygalifolia

By Jeff Howes, edited Dan Clarke