The "Telstar" varieties of Dianthus are a cross between the annual Dianthus chinensis, and the biennial Dianthus barbatus.  You wouldn't think you could get a perennial by crossing an annual and a biennial!  It's only supposed to be perennial at the northern end of its range, though.  Telstar comes in several color combinations, including whites, pinks and reds.  The one pictured is called "Telstar Scarlet."  It blooms heavily starting in mid-May, and continues to flower until frost.  It grows about 9" tall in my garden.