It is always nice to find a flower that really lives up to its description; Catananche caerulea is a lovely flower that really is sky blue. It grows about 40 cm (18") and although it is listed as a short-lived perennial - those I started from seed many years ago are still blooming away. The crown of the plant is low-growing and quite inconspicuous - the stems and flowers give this plant its height. It pairs beautifully with grasses. I've got mine growing next to a Carex muskingumensis.
Because of its long stems it dances in the wind in concert with the grass. Apparently it was used in love potions - hence its common name of Cupid's Dart.