Erect herbs or shrubs to 2 m tall, glabrous. Leaves long and narrow with numerous regularly spaced, short stalked leaflets; leaflets ca. 70-100, narrowly oblong, rounded at both ends, mucronate at the apex, to 25 mm long, ca. 3 mm wide; petioles 5-10 mm long; petiolules to 1 mm long; rachis to ca. 20 cm long; stipules linear to lanceolate, acuminate, to 5 mm long, apparently deciduous. Inflorescences axillary racemes with 3-5 flowers on thin pedicels ca. 10 mm long. Flowers 12-18 mm long; hypanthium broad campanulate, to 5 mm wide, ca. 5 mm long, including the calyx teeth, the teeth 1.0-1.5 mm long, triangular with abruptly acuminate tips; standard suborbicular, ca. 15 mm wide and long with raised appendages at the base of the blade, short clawed; wing petals oblong, ca.
15 mm long, short clawed; keel petals slightly shorter than the other petals, upcurved; stamens with free portion of filaments alternately unequal. Fruit long and narrow, to 25 cm long, 3-4 mm wide, beaked, stipitate, the margins thick- ened, glabrous; seeds numerous, oblong, 3-4 mm long.
Sesbania emerus is found in fields and wet ground in Panama and northward throughout Central America. It is also found in the West Indies.