Houstonia (genus)

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Bluets (Houstonia caerulea) Hedyotis caerulea.jpg
Houstonia caerulea
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Gentianales
Family: Rubiaceae
Subfamily: Rubioideae
Tribe: Spermacoceae
Genus: Houstonia

See text.

  • Poiretia J.F.Gmel. non Vent.
  • Panetos Raf.
  • Chamisme Nieuwl.

Houstonia (Bluet) is a genus of plants in the Rubiaceae family. Many species were formerly placed (along with other now-segregate genera) in a more inclusive Hedyotis.

Bluets are often small and delicate. For example, H. rosea may attain a height of only one inch. Some species have a single-stem, while others are more "bunchy." Flowers may be blue, purple, lavender, white, or rose, often with shades of one color present in a single population. Flowers have four sepals, a salverform corolla with four lobes, and an inferior ovary. Some species exhibit heterostyly. The fruit is many-seeded capsule which usually dehisces via a suture across the apex; often the capsule is roughly heart-shaped.

Houstonia consists of 20 species native to North America.[2] Another five species are classified in the genus Stenaria (Houstonia without Stenaria is paraphyletic).[3] Close relatives of the genus are Oldenlandia microtheca and, more distantly, Arcytophyllum.[4]


Species accepted as of May 2014:[5]


  1. ^ "World Checklist of Selected Plant Families". 
  2. ^ Edward E. Terrell (Jun 10, 1996), "Revision of Houstonia (Rubiaceae-Hedyotideae)", Systematic Botany Monographs (American Society of Plant Taxonomists) 48: 1–118, doi:10.2307/25027862, JSTOR 25027862 
  3. ^ Sheri A. Church and Douglas R. Taylor (2005), "Speciation and hybridization among Houstonia (Rubiaceae) species: the influence of polyploidy on reticulate evolution", American Journal of Botany 92 (8): 1372–1380, doi:10.3732/ajb.92.8.1372 
  4. ^ Groeninckx, I., Dessein, S., Ochoterena, H., Persson, C., Motley, T.J., Kårehed, J., Bremer, B., Huysmans, S., Smets, E. (2009). "Phylogeny of the Herbaceous Tribe Spermacoceae (Rubiaceae) Based on Plastid DNA Data". Annals of the Missouri Botanical Garden 96 (1): 109–132. doi:10.3417/2006201. 
  5. ^ Kew World Checklist of Selected Plant Families