Any of several plants, especially of the genus Cassia , in the pea family (see legume ), mostly of subtropical and tropical regions.
Many are used medicinally; some yield tanbark used in preparing leather. Some sennas are among the showiest flowering trees. In the eastern U.S., wild sennas ( C. hebecarpa and C. marilandica ) grow up to 4 ft (1.25 m) high and have showy spikes of yellow flowers. Some species are Old World shrubs or small trees.