I moved into a house during the winter and have discovered rhubarb growing all around the building. It's out of control! There are so many plants that they have started popping up in the lawn! In early spring, a friend came over to gather some and used it for baking and said it wasn't very good. We assume the plants must be old. Yet they continue to grow, grow, grow! I've tried to dig them up but they are huge and obviously the roots go very deep. Sandy, is there anything I can sprinkle on the root to kill the plants?