Houstonia serpyllifolia, commonly called thymeleaf bluet, creeping bluet, mountain bluet, Appalachian bluet or Michaux's bluets is a species of plant in the coffee family (Rubiaceae). It is native to the eastern United States, where it is found in the central and southern Appalachian Mountains. It has been documented in the states of Pennsylvania, Maryland, West Virginia, western Virginia, North Carolina, South Carolina, Kentucky, Tennessee, Ohio, and northeastern Georgia.