Vascular Plants of North Carolina
Account for Longleaf Bluet + - Houstonia longifolia   Gaertner
Members of Rubiaceae:
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Section 6 » Order Rubiales » Family Rubiaceae
AuthorGaertner
DistributionScattered over most of the mountains and Piedmont, and sparingly ranging into the southwestern Coastal Plain, including in the Sandhills region. NOTE: Neither RAB (1968) nor NCU specimens verify records from the northeastern Piedmont. Thus, the cluster of records for the 6-county region from Person to Warren and south to Wake may refer to misidentified specimens of H. tenuifolia. They are retained on the range map only because the range in VA shows on the Digital Atlas of the Virginia Flora as occurring in nearly all counties in southern VA along the NC state line. Thus, the northeastern piedmont is surely within the overall species range.

This species has a very wide range, occurring from Canada south to western FL and OK, generally absent on the Coastal Plains except in Sandhills areas.
AbundanceGenerally uncommon to infrequent in the southern mountains and most of the Piedmont, including the Sandhills region of the Coastal Plain. Generally rare in the north-central and northeastern Piedmont (where the status is unsettled), and maybe absent in the northern mountains.
HabitatThis is a species of dry soil, often rather sandy. It occurs around rock outcrops, opening in dry woods and wooded borders, and in pine/scrub oak sandhills in the Sandhills region. It shows no affinity to circumneutral soil that the similar H. tenuifolia does.
See also Habitat Account for General Dry-Xeric Glades and Barrens
PhenologyBlooms from June to August, and fruits soon after flowering
IdentificationThis is a slender species, with several stems from a common base, growing to about 8" tall. Basal leaves are absent at flowering time, and thus the stem leaves are opposite, scattered, sessile, and linear to more often oblong, about 1.5" long and about 1/8" wide -- wider than in the very slender H. tenuifolia. At the end of each stem is a short branched inflorescence of cymes, with each flower being a bit tubular with flared lobes, white to very light lavender-white, about 1/4" long and wide at the 4 spreading petals. The similar and easily confused H. tenuifolia has leaves narrower, needle-like and barely 1/10" wide, and the flowers are on longer pedicels, about 2/5" long as opposed to nearly sessile in H. longifolia. Though neither is scarce in the state, be careful separating these two, as both grow in dry and typically sandy soil, often near rocks.
Taxonomic CommentsWeakley (2018) lists two varieties -- the main one in the state being var. compacta, and var. glabra, which is limited to the southwestern mountains.

Other Common Name(s)Longleaf Summer Bluet
State RankS3 [S3S4]
Global RankG5
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