The genus Boronia is one of the best known of all Australian plants. There are approximately 95 species, all but one of which occur only in Australia. The majority of species are found in south-western Australia.
B.pinnata is a small shrub up to about 1.5 metres in height. The flowers are 4-petalled of a star-like appearance and usually pale to deep pink in colour. White flowered forms are known and are in cultivation. The flowers which appear in spring are well displayed in the upper leaf axils and are about 15 mm in diameter. The foliage is pinnate (compound leaves made up of a number of leaflets – in this case usually 5 to 9 leaflets) with leaves to around 25 – 50 mm long. The leaves contain aromatic oils and produce a very strong aroma when crushed. B.pinnata is similar to B.thujona which usually has more leaflets with slightly toothed margins.
This species has been in cultivation for many years and is a very desirable garden plant. Unlike many other boronias, it is a hardy species for temperate climates in well drained, moist soils, preferably in semi shade. It should not be allowed to dry out.
In common with most members of the Rutaceae, propagation of B.pinnata from seed is difficult but cuttings usually strike readily from current season’s growth.
Photo: Brian Walters