Brachychiton is a genus of approximately 31 species of trees and large shrubs in the family Malvaceae (order Malvales), commonly known as kurrajong or bottletree. The genus is overwhelmingly Australian, with 30 of its species endemic to the continent and one extending to New Guinea. Fossil evidence from New South Wales and New Zealand dates the lineage to around 50 million years ago, placing its origins in the Paleogene.
Plants range in height from 4 to 30 metres. Several species are pachycaul — their trunks are conspicuously swollen relative to overall plant size, functioning as water-storage organs that sustain the tree through seasonal drought. Some species are dry-season deciduous, shedding leaves during the driest part of the year; eastern forest species typically drop their foliage before flowering, while those of drier regions carry flowers and leaves simultaneously. Leaves show considerable variation even within species, ranging from undivided (entire) to deeply palmately lobed with long, slender lobes joined only at the base; they measure 4–20 cm in both length and width.
All species are monoecious, bearing separate male and female flowers on the same individual. The flowers lack true petals; instead, a bell-shaped, brightly coloured calyx of fused lobes serves as the visual attraction for pollinators. Female flowers each have five separate carpels, each capable of developing into a woody follicle enclosing several seeds. Flower colour is often variable within a species. The seeds are surrounded by loose seed coats — the feature that inspired the genus name.
In cultivation, a handful of species — including the widely grown Illawarra flame tree (Brachychiton acerifolius) — have been established as ornamental garden trees in hot, dry climates around the world, including the Mediterranean region, South Africa, and the western United States. Hybrids between species have also been produced for horticultural use.
Etymology
The name Brachychiton is derived from the Greek brachys (short) and chiton (tunic), a reference to the loose seed coats surrounding the seeds. The common name "kurrajong" comes from the Dharuk word garrajuŋ, meaning "fishing line," reflecting the traditional use of the fibrous inner bark by Aboriginal Australians to make fishing lines and cordage.
Distribution
Brachychiton is native to Australia, which is the centre of the genus's diversity with 30 of the approximately 31 species, and extends to New Guinea with one species. Within Australia the genus occurs across a wide range of habitats from tropical and subtropical forests to arid and semi-arid inland regions. In cultivation, several species have been successfully established outside their native range, including in the Mediterranean basin, South Africa, and the western United States.
Cultivation
A few Brachychiton species are widely grown as ornamental trees, valued for their drought tolerance and, in the case of B. acerifolius, spectacular seasonal flowering. They have been introduced to hot, dry regions including the Mediterranean, South Africa, and the western United States. Kurrajongs are noted for blooming erratically in cultivation. Interspecific hybrids, such as B. ×populneo-acerifolius, have been developed for horticultural use.
Cultural Uses
The fibrous bark of kurrajong trees was used by Aboriginal Australians to make fishing lines and cordage — the origin of the common name "kurrajong" from the Dharuk word garrajuŋ (fishing line). Seeds of several species are edible and were a food source for Indigenous Australians.
