These are hairy, coarse-looking plants, often with several to many stems arising from a crown. The corolla is reddish to maroon, and the fruits are orange to red.

1. Principal mid-cauline leaves tapered to narrow base (but upper leaves often narrowly connate); stem pubescence often chiefly of long (ca. 1–2 mm) eglandular hairs (usually with some short eglandular or gland-tipped hairs besides); style equaling or slightly shorter than the corolla (rarely exserted).

T. aurantiacum

1. Principal mid-cauline leaves both ca. 3–5 cm broad at the base and connate (upper leaves merely tapered basally); stem pubescence all or mostly of ± dense, short (0.5 mm or less), gland-tipped hairs; style exserted beyond the corolla.

T. perfoliatum

All species found in Triosteum

Triosteum aurantiacumHORSE-GENTIAN 
Triosteum perfoliatumHORSE-GENTIAN 


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 29, 2017.