Can you help me identify this plant?
I have a mystery plant that I need help identifying. You can see a picture of it at my photo site. The plant in question is at the front left of the picture, alongside the stream. This picture was taken last May, the plant has grown rather quickly...I'd say it's probably 2 or 3 times as thick and much taller now. The foliage is evergreen, with a spring/summer pale yellow flower about the size of a silver dollar. The foliage is now 24-36 inches tall on some of my plants.
The landscaper who installed the plants referred to it as Louisiana Iris, but our horticulturist at LSU Ag Center here in West Monroe said that it isn't. I would really appreciate any help anyone can give in naming this plant. Some of them are beginning to block my walkways and, until I have it identified, I'm not sure what my plant of action will be for controlling it. Thanks y'all!