Houstonia caerulea (azure bluet or Quaker ladies) is a perennial species in the family Rubiaceae. Houstonia caerulea produces showy flowers approximately 1 cm across. These flowers are four-parted with pale blue petals and a yellow center. The foliage is a basal rosette. Stems are up to 20 cm tall with one flower per stalk. It thrives in moist acidic soils in shady areas, growing especially well among grasses.