Boronia ‘Carousel’ has an obscure origin. It was possibly originally selected from the wild in the Albany district of Western Australia. The cultivar is reputed to be a hybrid between B. molloyae and B. heterophylla. This hybrid has been around for many years and was probably registered in 1987.
Boronia ‘Carousel’ is a tall shrub reaching two metres in height.
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 cultivar, the leaves are compound-pinnate, aromatic, dark green and up to 35 millimetres long with leaflets about 10 mm long.
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 cultivar, flowers are bell shaped, to 8 mm long, bright pink aging to deep red and are both conspicuous and profuse. Flowering occurs from late September to November.
Light pruning is beneficial after flowering. This is a very handsome boronia and appears to carry more flowers than its supposed parent, B. heterophylla. It is commonly sold, even at large mainstream nurseries and also sold overseas.
Certainly our plant has foliage and flowers similar to B. heterophylla.
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.
This cultivar would have to be propagated from cuttings to retain the characteristics of the cultivar.
Boronias will likely die in a fire and regenerate from the seed bank.
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 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.
‘Carousel’ – reason for this name is not fully known. Possibly named for the round nature of the flowers.
Trigg Plants – Boronia ‘Carousel’ profile page https://triggplants.com.au/product/boronia-heterophylla-pixie-in-75mm-supergro-tube-copy/
Australian Cultivar Registration Authority – Boronia ‘Carousel’ profile page https://acra.biodiversity.services/info/rdetail/530