Houstonia (bluet) is a genus of plants in the family Rubiaceae. Many species were formerly classified, along with other genera since segregated elsewhere, in a more inclusive genus Hedyotis. Bluets are often small and delicate. For example, H. rosea may grow only one inch tall. Some species are single stemmed and others have multiple stems in bunches. Flowers are blue, purple, lavender, white, or rose, often with shades of one color present in an individual population. Flowers have 4 sepals, colloquially denominated "petals", a salverform corolla with 4 lobes, and an inferior ovary. Some species exhibit heterostyly. The fruit is an often roughly cordate capsule enclosing many seeds and which usually dehisces via a suture across its apex. Houstonia consists of 20 species native to North America. Another 5 species are classified in the genus Stenaria; Houstonia without Stenaria is paraphyletic. Close relatives of the genus are Oldenlandia microtheca and, more distantly, Arcytophyllum. Its members superficially resembles species of the genus Myosotis (Forget-me-nots), but are distinguished from the latter by having only 4 sepals (petals) instead of 5.

Species

Species accepted as of May 2014 are: