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Venus' Pride, Large Bluet, Large Houstonia, Summer Bluet, Purple Bluet - Houstonia purpurea


Family: Rubiaceae - Madder family Genus Common Name: Bluets Native Status: Native
Houstonia purpurea - Venus' Pride, Large Bluet, Large Houstonia, Summer Bluet, Purple Bluet. Houstonia purpurea is in a group of Houstonia species with multiple flowers in the inflorescence - subgenus Chamisme. My experience with Bluets prior to identifying this plant was with the smaller bluets with solitary flowers on usually terminal pedicels - H. caerulea and H. pusilla. Two of the three varieties of this species, H. purpurea var. purpurea and var. calycosa, are found throughout much of the eastern half of the United States. The third variety, var. montana - Roan Mountain Bluet - is found only in a small area of the Appalachian Mountains on the Tennessee / North Carolina border.

Houstonia purpurea var. montana is a U.S. endangered species. Some authorities recognize it as a separate species, Houstonia montana. While the other two varieties can be quite common in parts of their ranges, var. calycosa is listed as Endangered in New York, and var. purpurea is Endangered in North Carolina. Var. purpurea is presented in these photographs.

Found in:
AL, AR, CT, DC, DE, FL, GA, IA, IL, IN, KY, LA, MA, MD, ME, MI, MO, MS, NC, NE, NJ, NY, OH, OK, PA, SC, TN, TX, VA, VT, WV

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Houstonia purpurea

Distribution of Houstonia purpurea in the United States and Canada:
USDA Plants Distribution Map temporarily unavailable.
Blue=Native; Grey=Introduced

Map from USDA Plants Database:
USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov, 25 Feb 2017). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

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Site: Ascalon Road, Walker County, GA Date: 2013-June-07Photographer: Gerald C. Williamson
Nikon D7000
Tamron SP 90MM f/2.8 AF Macro
The flowers of Houstonia purpurea are white to purple or lavender. The corolla has a tube and four lobes. (Interestingly, 2 of the flowers on this plant have 5 lobes.) The inflorescence contains several flowers.
Houstonia purpurea

Site: Ascalon Road, Walker County, GA Date: 2013-June-07Photographer: Gerald C Williamson
Nikon D7000
This photograph shows two features I used to decide this was var. purpurea rather than var. calycosa - sepal length and leaf width. The sepals of var. purpurea are generally less than half the length of the flower, while those of var. calycosa are slightly less than half the length of the flower to about ¾ the length. The leaves of var. calycosa are smaller and relatively narrower than those of var. purpurea.
Click on the photo for a larger image
Houstonia purpurea

Site: Ascalon Road, Walker County, GA Date: 2013-June-07Photographer: Gerald C Williamson
Nikon D7000
Houstonia purpurea grows to about 20 inches tall. The inflorescence is terminal on one to several branches.
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Houstonia purpurea

Site: Ascalon Road, Walker County, GA Date: 2013-June-07Photographer: Gerald C Williamson
The stem leaves are opposite, sessile, and have 3 to 5 main veins. There are basal leaves which are absent at flowering. The stems are variously hairy.
Click on the photo for a larger image
Houstonia purpurea

Site: Ascalon Road, Walker County, GA Date: 2013-June-07Photographer: Gerald C Williamson
Nikon D7000
If it branches (usually,) Houstonia purpurea branches at the leaf nodes. I find the stipules interesting, and wonder if they are only present at nodes with branches.
Click on the photo for a larger image
Houstonia purpurea

References used for identification and information:

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All content except USDA Plants Database map Copyright Gerald C. Williamson 2017
Photographs Copyright owned by the named photographer