Rhubarb is a plant that belongs to the genus ‘Rheum’ in the family ‘Polygonaceae’. Rhubarb leaves contain poisonous substances, including oxalic acid, which is a nephrotoxic and corrosive acid that is present in many plants. Cooking the leaves with soda can make them more poisonous by producing soluble oxalates. However, the leaves are believed to contain an additional, unidentified toxin. Although the leaves are toxic, various parts of the plants have medicinal and culinary uses.