Houstonia caerulea

Houstonia caerulea (azure bluet or Quaker ladies) is a perennial species in the family Rubiaceae. It is native to eastern Canada (Ontario to Newfoundland) and the eastern United States (Maine to Wisconsin, south to Florida and Louisiana, with scattered populations in Oklahoma).
Description.
"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.