A cathartic plant is a type of plant that has a purgative effect on the body, often used to treat constipation. The three crossword solutions for this term are SENNA (5 letters), Epsom (5 letters), and PHYSIC (6 letters). SENNA is a genus of flowering plants in the legume family, native to tropical regions of the world. Epsom is a town in Surrey, England, known for its natural spring water containing magnesium sulfate, which is used as a laxative. PHYSIC is an old-fashioned term for a medicinal herb or plant, usually used to treat digestive issues.