B. australis is an herbaceous perennial that reproduces both sexually and asexually by means of its spreading rhizomes . The plants are erect and emerge from the rhizomatic network. The roots themselves are branched and deep, which helps the plant withstand periods of drought. When dug up they are woody and black in colour and show tubercles , wart-like projections found on the roots. The plants branch extensively about halfway up. The stems are stour and glabrous, or hairless. If they are broken, a sap will be secreted that turns a dark blue upon contact to the air. The trifoliate leaves are a grey-green in colour and are arranged alternately. The leaves are further divided into clover-like leaflets that are obovate in shape, or wider towards the apex. Flower spikes appear in June. Emerging at the pinnacle ar short, upright terminal racemes that have pea -like flowers that vary in colour from light blue to deep violet. The flowers, which bloom from April through August depending on the region, are bisexual and are roughly 2.5 cm long (1 inch). The fruit is a bluish black inflated and hardenend pod that ranges from 2.5 to 7.5 cm in length (1 to 3 inches) by 1.25 to 2.5 cm (0.5 to 1 inch). They are oblong in shape and are sharply tipped at the apex. At maturity they will contain many loose seeds within. The seeds are yellowish brown, kidney shaped and about 2 mm (0.08 inches) in size.The leaves emerge about one month before flowering and are shed approximately one month after the pods form. Once the seeds are fully mature, the stems turn a silverish grey and break off from the roots. The pods stay attached and are blown with the stems to another location.