Horse Gentian is a native erect perennial forb growing from 2 to 4 feet high on stout green unbranched slightly ridged stems that have many short glandular hairs.
The leaves are opposite, ovate to egg shaped, 5 to 10 inches long, and appear connected at the base. The lower most leaves will appear to be pierced by the stem. Each pair of leaves is placed 90 degrees to the adjacent upper and lower pair. The leaf margins are entire but undulating. The upper surface is a dull green with some hair while the lower surface is paler with more fine hair.
The inflorescence is a cluster of 1 to 6+ small flowers in the leaf axils.
The flowers are 5-parted, stalkless, with a tubular shape. The corolla is a reddish-purple with lobes that are fairly equal, rounded at the tips and glandular-hairy on the outside. The green calyx has five linear pointed glandular-hairy lobes that are as long as the corolla. These lobes are about the same color as the corolla but turn green in fruit. These spread outward when the flower opens. There are 5 stamens with yellow anthers that do not show beyond the corolla lobes, but the single style, greenish-yellow, is exserted beyond the lobes and has a 3-lobed stigma at the tip. The ovary located at the base of the flower is 3-celled.
Fruit: Fertile flowers produce an ovoid to roundish drupe, between 1/3 and 1/2 inch in size, covered with glandular hair and faintly showing 3 section lines; the drupe turns from a greenish-yellow to an orange-yellow in the fall with the sepals persistent. In Autumn these are quite noticeable in the leaf axils. Each drupe contains 3 hard 3-angled nutlets, ridged and rounded on one side and flat and concave on the other, about 7 x 5 mm in size.
Habitat: Horse Gentian grows in dry areas of woods, thickets, and open abandoned areas, preferring poorer soils, adapts to sun, partial shade or shade, and mesic to mesic-dry conditions. The plant produces a taproot and propagates by re-seeding itself in the wild but is difficult to start from seed.
Names: The "horse" of the common names refers to the general coarseness of the plant. The genus name Triosteum, is derived from Greek words tri, meaning 'three' and osteon, meaning 'bone', together meaning "three bones" and referring to the 3 hard nutlets in the fruit which have bony ridges. The species name, perfoliatum, is derived from the Latin meaning 'through the leaf' referring to the stem piercing the lower leaves of this species. The author name for the plant classification, 'L.', refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. Even though most of the common names title the plant as a 'Gentian', the species is not in the Gentian Family. As to "wild coffee" and "feverwort", see notes at page bottom.
Comparison: A very similar species is Early Horse Gentian (or Orange-fruit or Scarlet-fruit Horse Gentian), T. aurantiacum, the difference being the lower leaves are not pierced by the stem, the style of the flower is not as exserted (but this is not determining) and the fruits are more orange-scarlet in color.
Above: The flowers appear in the leaf axil. Note the leaf pairs placed 90 degrees from adjacent pairs. The flowers have glandular hair on the calyx lobes and outer lobes of the corolla. The yellow-green style is exserted from the corolla while the stamens remain inside. The reddish-purple flowers typically bloom in early June.
Below: The green sepals of the calyx are persistent onto the fruit. These drupes turn to a yellow-orange color in late summer. They retain a coating of fine hair. Inside each drupe are 3 hard nutlets.
Below: 1st photo - The stem is ridged and covered with fine glandular tipped hair. 2nd photo - The underside of the leaf is paler in color with fine hair, particularly on all the ribs and veins.
Below: 1st photo - The arrangement of the flowers around the leaf axils. There can be up to 6+ flowers (6 as shown here); on the one in front the corolla tube has dropped of leaving the spreading lobes of the calyx. Not the glandular hair. 2nd photo - A lower stem leaf showing the leaf node where the stems appears to pierce the clasping leaves.
Below: The dark nutlets in fresh condition. Colors fade as they dry. One side is flat and concave, the other sides rounded and ridged, 7 x 5 mm.
Notes: T. perfoliatum is indigenous to the Garden. Eloise Butler noted T. perfoliatum in her Garden Log on Sept. 7, 1907. She also reported planting specimens obtained from a source in Frontenac, MN in 1911. Martha Crone planted seeds in 1944, '45 and '53 without listing the species, and plants in 1950, but she did not list the plant on her 1951 inventory of plants in the Garden at that time, instead she reported the "Scarlet-fruited Horse Gentian," T. aurantiacum. By the time of the 1986 census, T. perfoliatum was once again reported in the Upland Garden. The plant is native to Minnesota in a string of counties that run from the SE Corner, through Dakota and Hennepin and into the central part of the state. In North America it is found in the eastern half excepting the gulf coast states in the U.S. Canada reports it in Ontario, Quebec, New Brunswick and Nova Scotia. T. perfoliatum and T. aurantiacum are the only species of Triosteum found in Minnesota.
Common Names and Uses: The common name of Wild Coffee is best explained by Merritt Fernald (Ref.#6) when he wrote: "Barton, a distinguished botanist of Philadelphia a century and more ago, wrote: 'I learned from the late Rev. Dr. Muhlenberg, that the dried and toasted berries of this plant, were considered by some of the Germans of Lancaster County, as an excellent substitute for coffee, when prepared in the same way. Hence the name of wild coffee, by which he informed me it was sometimes known' ". Fernald states that the information applies to all three native species of Triosteum. The Dr. Muhlenberg refered to is Gotthilf Heinrich Ernst Muhlenberg (1753-1815) a U.S. citizen and German educated botanist who produced several catalogues of plants after retiring as a Lutheran pastor. He is the recognized classification author of a number of plant species. Barton is Benjamin H. Barton co-author in 1877 of The British Flora Medica.
Mrs Grieve (Ref. #7) notes that the common name 'Feverwort or Feverroot' comes from the plant sometimes being called a Ginseng, which plant is commonly used for medicinal treatments. She also reports the the root of the plant is sometimes mixed in with those of Senega, Polygala senega, whose root has strong medicinal qualities.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"