Plant of the Week

Map of the United States showing states. States are colored green where the species may be found.
Triosteum aurantiacum range map. USDA PLANTS Database.

Axillary flowers of Triosteum aurantiacum.
Axillary flowers of Triosteum aurantiacum. Photo by Merel R. Black, Robert W. Freckmann Herbarium, University of Wisconsin-Stevens Point.

Orange fruits of Triosteum aurantiacum.
Orange fruits of Triosteum aurantiacum. Photo by Christopher Noll, Robert W. Freckmann Herbarium, University of Wisconsin-Stevens Point.

Orange-Fruited Horse Gentian.
Triosteum aurantiacum, Orange-Fruited Horse Gentian. Photo by Merel R. Black, Robert W. Freckmann Herbarium, University of Wisconsin-Stevens Point.

Orange-Fruited Horse Gentian (Triosteum aurantiacum)

By Samuel Hein, Chequamegon-Nicolet National Forest

Orange-fruited horse gentian, Triosteum aurantiacum, is a member of the honeysuckle family (Caprifoliaceae), which has 5 genera and about 220 species of mostly woody shrubs and vines. The honeysuckle family is mostly known for ornamental shrubs and vines. The genus Triosteum has six species native to North America and Eastern Asia. It is not a true gentian, as it has different fruit and flower structures and has stipules. True gentians belong to the gentian family, Gentianaceae.

Triosteum is derived from Greek, meaning “three bones” and aurantiacum is Latin, meaning “orange-colored”. There are 3 to 4 dull purple or red flowers in each leaf axil that yield oblong orange fruits, each containing 3 hard stones. The flowers bloom late spring to early summer and the fruits ripen in the fall. They thrive in rich, well-drained soils and soil rich in organic matter. Orange-fruited horse gentian grows in rocky woods, thickets, stands of oak, aspen, sassafras, and/or pines. The "horse" of the common name refers to the general coarseness of the plant. A very similar species is wild coffee or feverwort, Triosteum perfoliatum, the difference being the stem in wild coffee pierces the leaves.

Orange-Fruited Horse Gentian has light green stems and large, broad, oval shaped green leaves, growing 2 to 4 feet tall. The leaves attach to the stem by narrow leaf connectors and rotate 90 degrees from the previous set of leaves. Its flowers attract long-tongued pollinators, especially bumblebee (Bombus spp.) and Anthophorid bees (Anthophora spp.). The caterpillars of the moth Hemaris diffinis (snowberry clearwing) feed on Triosteum spp. and other members of the honeysuckle family.

Horse gentians were traditionally valued for their medicinal properties. They were used by Native Americans for urinary pain and applied topically to sores and swollen areas. Roots were used to treat fevers, induce vomiting, and were a powerful laxative. The berries, when roasted and dried, can be used as a substitute to coffee.

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