Senna (from san), the sennas, is a large of around 250 of in the family , subfamily . This genus is native throughout the , with a small number of species reaching into regions. Almost all species were at one time or another placed in , a close relative which until recent decades served as a "" to hold all . The species were reassigned by and , but this process is not entirely complete and some corrections may still take place.
Typically Senna species have yellowish flowers. They may be , smallish or even a kind of , but typically are or . They are and offer as a reward (the flowers supply no nectar to pollinators).