spice or flavor-producing plant senna plant Senna spp. Senna Senna Mill. PLANTS:SENNA Senna , the sennas, is a large genus of flowering plants in the legume family *Fabaceae*, and the subfamily Caesalpinioideae. This diverse genus is native throughout the tropics, with a small number of species in temperate regions. The number of species is estimated to be from about 260 to 350. The type species for the genus is Senna alexandrina. About 50 species of Senna are known in cultivation. Cassia gum, an extract of the seeds of Chinese senna (*S. obtusifolia*), is used as a thickening agent. The leaves and flowers of Siamese cassia (*S. siamea *) are used in some Southeast Asian cuisines, such as Thai and Lao cuisines. [https://en.wikipedia.org/wiki/Senna_(plant)] cassia spp. senna spp. requires discussion