I've seen old cars buried behind barns and just about anything one can imagine. Some farmers used to spray around the barn quite heavily for flies or would use that spot to dump all kinds of waste oil, gasoline used to wash engine parts, etc. You could possibly have picked a toxic location.
Does the rhubarb have the direct sunlight and water it needs?
You could try mulching it good in the late fall with compost to see what happens or move some dormant split roots to a new location.
I've seen old cars buried behind barns and just about anything one can imagine. Some farmers used to spray around the barn quite heavily for flies or would use that spot to dump all kinds of waste oil, gasoline used to wash engine parts, etc. You could possibly have picked a toxic location.
Does the rhubarb have the direct sunlight and water it needs?
You could try mulching it good in the late fall with compost to see what happens or move some dormant split roots to a new location.