7. Rhubarb Leaves
While rhubarb stalks are a popular dessert ingredient, the leaves contain oxalic acid and anthraquinone glycosides, both of which are toxic. Ingesting large amounts can cause difficulty breathing, seizures, and kidney failure. The good news is that the stalks remain perfectly safe and delicious when cooked into pies, jams, and sauces. Always discard the leaves and never attempt to eat or cook them.
How to enjoy without risk: Trim stalks carefully and throw away all leaves.