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Boronia ledifolia

Showy Boronia, Sydney Boronia, Ledum Boronia

Family: Rutaceae

A shrub to 1.5 metres tall by up to 1 metre wide.

Naturally found in heath and dry sclerophyll woodland and forest, especially on Hawkesbury Sandstone and granite soils.

Much of its distribution is in the Central Coast subdivision of NSW; but it extends into the south coast (to Moruya and west of Narooma); with a distjunction to north-eastern Victoria, as well as the central tablelands and western slopes  of NSW, with a disjunct population on the Northern Tablelands which may be a different species.

It grows naturally in moist, semi shaded positions with free draining lighter soils. Very showy in sandstone woodlands when in flower. In some seasons, it can be conspicuous on the Hawkesbury Sandstone cliffs above the Pacific Highway between Sydney and Gosford.

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 is one that produces both forms: leaves can be singular or produced as a pinnate leaf with 3 to 7 leaflets. Leaves have a very strong odour when crushed, that some find unpleasant and vary from 4 to 35 mm long.

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 leaf axils, usually on their own or in clusters (cymes). Flowers are very showy. White flowering and multi-petal flowering forms are also found in the wild; seed in July–October (usually peaking in August-September).

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.

In the garden

A desirable garden plant in flower from late winter. This species requires a moist and well drained situation and not allowed to dry out for garden situations.

Tends to be short-lived in cultivation. Growing life can be extended in pots as environmental factors can be controlled better.

Propagation

Propagation of B. ledifolia from seed is difficult. Propagation from cuttings of current season’s growth can be slow to strike as well, but is an effective method.

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.

Other information

Typically, boronias would die in a fire and regenerate from the seedbank.

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 Fransesco 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 material.

ledifolia – Latin referring to the genus Ledum and folia – “leaves”, a reference to the appearance of the foliage of Ledum spp. – a genus now recognised as part of Rhododendron.

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

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

Australia Native Plants Society Australia – Boronia ledifolia profile page https://anpsa.org.au/plant_profiles/boronia-ledifolia/

Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.

 

By Jeff Howes. Editing and additional text by Dan Clarke.