The rhubarb leaves are considered toxic as they contain u003ca href=u0022https://www.bhg.com/recipes/how-to/cook-with-fruits-and-vegetables/rhubarb-basics/u0022 target=u0022_blanku0022 rel=u0022noreferrer noopeneru0022u003ea toxin called oxalic acidu003c/au003e. So make sure to trim them away.