I have a magnificent 200-year-old sycamore tree that is very happy to be in an area that floods occasionally (a few days at a time) in the spring. However, the area underneath it is a mudhole in the spring and a dustbowl in the summer. What kind of groundcover can tolerate deep shade and a bit of flooding? Someone suggested Creeping Jenny but I'm not wild about the yellow color. Is there any kind of grass that might grow there? Thanks for any suggestions!