Another great old fashioned plant - Rose Mallow (Hibiscus moscheutos) has the largest flower of any perennial (didn't know this). It can reach a height of 8 feet and have a spread of 3-6 feet. Mine are really tall and so, so pretty. Cut the stems back in early spring and that's all the maintenance they need.
They're show stoppers in the garden! I did read they're deer resistant (for those of you that have those critters hanging around eating everything in sight).