Houstonia caerulea, commonly known as azure bluet, Quaker ladies, or bluets, 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). It is found in a variety of habitats such as cliffs, alpine zones, forests, meadows and shores of rivers or lakes.

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