Perennial herb with an upright, hairy stalk. Flowers clustered in leaf axils on very short stems, almost hidden by green calyx, tubular with 5 small lobes, reddish brown. Blooms May–July. Leaves opposite, the middle 3–5 pairs joined around the stem (perfoliate), broadly lanceolate, with smooth margins. Fruit berries that resemble little oranges, remaining on the stalks through fall.
Similar species: Two other horse gentians grow in Missouri. Yellow-flowered horse gentian (T. angustifolium), found in the Ozarks, has narrower leaves that are sessile or have winged stems (leaves are not perfoliate) and yellow flowers (sometimes orange to red). Red-fruited horse gentian (T. aurantiacum), scattered mostly in the eastern half of the state, is only weakly perfoliate, with leaves much narrower at the base, and has orange to red fruits. It can be hard to distinguish from T. perfoliatum.
Height: to 4 feet.
Bottomland forests, rich upland forests, bases and ledges of bluffs, edges of glades, and banks of streams and rivers; also roadsides. This is the most abundant and widespread horse gentian in our state.
Scattered nearly statewide. Most abundant in the Ozark and Ozark Border divisions.
Despite what the common names implies, this is not a true gentian (in the gentian family, the Gentianaceae). What’s going on? The word “horse,” as a plant adjective, implies something large, strong, or coarse. Similar plant names are horse-chestnut, related to buckeyes, and not in the beech family like edible true chestnuts; horse nettle, a prickly nightshade and not a true nettle (Urticaceae); and horseradish, which, though in the same family as radishes, is considerably stronger than them!
Pennsylvania settlers, and probably others, dried and roasted the ripe fruits of horse gentian and used the product as a coffee substitute, which explains one of the common names for this plant, “wild coffee.”
This and some other members of the honeysuckle family are larval host plants for the snowberry clearwing, a sphinx moth famous for its beelike coloration and for resembling a hummingbird as it visits flowers. Horse gentian flowers are pollinated by bumblebees and other long-tongued insects.
A very simple way of thinking about the green world is to divide the vascular plants into two groups: woody and nonwoody (or herbaceous). But this is an artificial division; many plant families include some species that are woody and some that are not. The diversity of nonwoody vascular plants is staggering! Think of all the ferns, grasses, sedges, lilies, peas, sunflowers, nightshades, milkweeds, mustards, mints, and mallows — weeds and wildflowers — and many more!