toadshade

Trillium sessile is a perennial, clump-forming herbaceous plant with a thick underground rhizome. Like all trilliums, it has a whorl of three bracts (leaves) and a single trimerous flower with 3 sepals, 3 petals, two whorls of 3 stamens each, and 3 carpels (fused into a single ovary with 3 stigmas). A single plant has one or two erect scapes (stems) per rhizome, each scape up to 25 cm (9.8 in) tall. The sessile (stalkless) bracts are elliptic, up to 10 cm (3.9 in) long and 8 cm (3.1 in) wide. The bracts may or may not be mottled. The erect, sessile flower nestled in the middle of the three bracts has a spicy, pungent odor. The sepals are mostly green but often streaked with purple along the edges or at the base of each sepal. The average length and width of a sepal is 21 mm (0.8 in) and 5.7 mm (0.2 in), respectively. The petals are erect and long-lasting. Although their shape and color are variable, a typical plant will have elliptic, reddish-purple petals. The base of a petal is narrowed and, in some cases, will have a very short claw-like base about 2 mm (0.1 in) long. The average length and width of a petal is 24 mm (0.9 in) and 6.6 mm (0.3 in), respectively, just slightly larger than a sepal. The stamens are about half as long as the petals, with the filaments being less than half the length of the inward-facing anthers. …

Trillium sessile is endemic to the eastern half of the United States, ranging from Maryland in the east to the Ozarks in the heart of the Mississippi Basin, and from the southern Great Lakes region to northern Alabama. The species occurs in more U.S. states than any other sessile-flowered trillium:

East of the Mississippi River: Alabama, District of Columbia, Illinois, Indiana, Kentucky, Maryland, Michigan, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia West of the Mississippi River: Arkansas, Kansas, Missouri, Oklahoma It is most abundant in Ohio, Indiana, northern Kentucky, and Missouri, but it is strangely absent from central Illinois. This creates a distributional gap between the eastern and western subpopulations of the species. Plants from the western subpopulation (centered in Missouri) often have scapes (stems) that are taller and bracts (leaves) that are narrower than plants from the eastern subpopulation. It is not known if this geographical separation was induced by genetic or environmental factors. T. sessile is found in rich woods, particularly in limestone areas and on calcareous soils. It is also found on alluvial floodplains and riverbanks, and occasionally on less fertile soils. …

Trillium sessile flowers in April in most areas. In the southern part of its range it flowers as early as late March, while its northernmost populations may not flower until mid-May. In Tennessee, fruits were observed to ripen and drop off between June 20 and July 5. The above ground parts of the plant die back by mid-summer but may persist longer in areas that do not completely dry out. The foul smelling flowers attract its primary pollinators, flies and beetles. In general, Trillium species are myrmecochorous, that is, ants facilitate seed dispersal in most (if not all) species. Since the seeds of T. sessile have attached elaiosomes, presumably its seeds are dispersed by ants as well.

Although some accounts indicate that the cooked greens of this plant may be edible as an emergency food, the entire plant, and especially the root, is known to induce vomiting. The fruit is considered a suspected poison. Trillium sessile has been used medicinally to treat tumors. It is sometimes cited as having been used as a poultice for boils and as a panacea-like decoction, but this claim is doubtful since it is attributed to Native American tribes (the Yuki and the Wailaki) of California, where this plant is not known to occur. Trillium sessile is sometimes grown in woodland wildflower gardens. Like many trilliums, it often does not transplant successfully from the wild.