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Boronia barkeriana

Barker's Boronia

Family: Rutaceae

A small shrub to 1 metre tall but can spread to 1 metre wide, producing many stems from the base.
It grows solely in NSW, as far south as the Braidwood district, then occurring north-east through the Milton region and Jervis Bay, up into the Southern Highlands and west of Kiama, with disjunct occurrences in Sydney’s Royal National Park, the north of Sydney and then in the Blackheath region in the Blue Mountains and east of Kandos. (There is one single record much further north in Dorrigo National Park).
It is typically found in moist heath, shrubland and 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 appear simple (although they are described as compound with 1 leaflet). These “leaves” (leaflets) are to 35 mm long and 10 mm wide with finely toothed margins, often with red colouring on margins and undersides, green to blue-green / grey-green in colour.

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, flowers are produced in the leaf axils, in groups of up to 8, occurring from September to December.

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 capsules are glabrous, about 4 mm long and 2 mm wide.



In the garden

Not much is known currently about the cultivation of this species and it is not commonly grown. It may be that it is difficult to grow or has not been trialled sufficiently to verify cultivation potential. It may become more readily cultivated in the future.

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.

Propagation

Boronias can be propagated from cuttings but with limited success with most but not all species.

Other information

There are three subspecies currently recognised in NSW:
Boronia barkeriana subsp. angustifolia, mainly growing in Morton and Budderoo National Parks with narrow leaves and without much toothing, as well as narrow sepals.
Boronia barkeriana subsp. barkeriana, growing on the coast and ranges over most of the range, with toothed leaves and narrow sepals
• Boronia barkeriana subsp. gymnopetala, only known from the area between Port Jackson and Waterfall but has not been collected since 1923 and is presumed extinct, with wider sepals and toothed leaves.

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 by fire and regenerate from the seedbank.

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.
barkeriana – Honours “Mrs. C.A. Barker” who collected a specimen near Mount Wilson in New South Wales, with the name published by Ferdinand von Mueller in 1880.

Not considered at risk in the wild. Although one of the subspecies is presumed extinct.

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

Wikipedia – Boronia barkeriana and Boronia profile pages
https://en.wikipedia.org/wiki/Boronia
https://en.wikipedia.org/wiki/Boronia_barkeriana


Gardening with Angus Website – Boronia for Beginners
https://www.gardeningwithangus.com.au/boronias-for-beginners-2/

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

By Jeff Howes, edited Dan Clarke