An erect, annual legume, subshrub, to about 3.5 m high, stems with spreading hairs when young, more or less glabrous later, terete or slightly angular. Leaves with 12 to 30 pairs of leaflets. Leaflets narrowly-oblong, apex obtuse or truncate-apiculate, 7 to 8 x 1.5 to 3 mm glabrous or with a few appressed hairs. Inflorescence a raceme of one to three (five) flowers. Pedicels more or less equal to the calyx. Calyx 3 to 4 mm long, the lobes up to about half as long as the tube. Corolla yellow. Standard conspicuously streaked on the back, 0.8 to 1.1 cm long. Pods slender, 12 to 20 x 0.25 to 0.3 cm, with a slender terminal point. Seeds dark brown, about 4 mm long.
Long confused with the Indian species S. aculeata, S. cannabina is essentially an Australian species, although it does occur northwards into Malaysia. In Australia, it is particularly common in subcoastal and adjacent areas of the northern states, but extends inland in some areas, especially Queensland, where it is widespread. It extends into South Australia along the Diamantina River, and into New South Wales along the Darling River. It is the most widespread of the Sesbania spp. and commonly grows in areas subject to inundation, where it is able to withstand waterlogged conditions. It can, at times, be a weed of irrigated rice fields and of low-lying wet cultivation paddocks.