Vascular Plants of North Carolina
Account for Yellowfruit Horse-gentian - Triosteum angustifolium   L.
Members of Caprifoliaceae:
Members of Triosteum with account distribution info or public map:
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Section 6 » Order Dipsacales » Family Caprifoliaceae
AuthorL.
DistributionRestricted to the Piedmont, and in this province limited to a NE-SW band through the east-central portions -- east to Granville and Chatham counties, and west to Caswell, Guilford, and Mecklenburg counties.

This is an Eastern and Mideastern species, ranging from NJ, PA, and MO south to central NC and northeastern TX.
AbundanceRare to locally uncommon; most numerous on the Durham diabase sill from Granville County to northern Durham County. This is a Watch List species.
HabitatThis is a species of dry to mesic edges and open woods, always over circumneutral soil. It grows in mafic barrens and glades, around outcrops, and wooded borders, over mafic rocks such as diabase, gabbro, and amphibolite.
PhenologyBlooms in April and May, and fruits from July to August.
IdentificationThis species is a medium-sized herb growing to 1.5-2' tall. It has several pairs of stem leaves, each elliptical in shape but with a clasping base, with the leaf blade gradually tapering to the base; each leaf averages about 4-5" long and 1.5" wide. In each leaf axil grows one or a few flowers, each tubular and nearly 1" long, with 5 short flaring lobes; each flower is light yellow. The fruit (drupe) is orange, ripening about 3 months after flowering. The only other Triosteum in its range in the state is the more numerous (though still infrequent) T. perfoliatum. That species is usually taller and more robust, has wider leaves that also are wide at the base where they clasp the stem (i.e., the blade does not narrowly taper to the stem), and flowers are maroon to purplish-brown in color, with a red to reddish-orange drupe. To find T. angustifolium, you need to locate sites over high pH soils, and look around wooded margins or openings in upland woods.
Taxonomic CommentsWeakley (2018) lists two varieties in NC -- the nominate var. angustifolium, and var. eamesii, but the latter seems to have only been reported in the state but not yet confirmed (in the mountains).

Other Common Name(s)Lesser Horse-gentian, Yellow Horse-gentian, Narrowleaf Horse-gentian
State RankS2
Global RankG5
State Status[W7]
US Status
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