This butter yellow, clump-forming perennial with Scabiosa-like flowers is for the back of the border, and there's good reason for it, too.  Cephalaria gigantea, or Giant Scabiosa,  can grow more than six feet high with a spread of nearly three feet, but don't let that deter you.  The deeply cut foliage stays low, while the flowers on wiry stems stand high.  The flowers make beautiful cut flowers, and they will keep going if you are vigilant about deadheading.  Cephalaria gigantea can easily be divided in spring or late summer.   Full sun/part shade, well-drained soil.  Zones 3-7.   (Photo by Franz Xaver, from Wiki Commons.)