Trillium erectum is a perennialherbaceous plant that grows to about in height with a spread of. It can tolerate extreme cold in winter, surviving temperatures down to. Like all trilliums, its parts are in groups of three, with a 3-petalled flower above a whorl of pointed triple leaves. The petals are usually dark reddish maroon to purplish, fading to purple with age, but petal color is variable with yellow, pale green, pink, or white petals occurring occasionally throughout the range of the species. The ovary is dark purple to maroon regardless of petal color. The carrion-scented flowers attract scavenging flies for pollination. Eventually the flower petals wither, leaving behind a fruit that ripens to a dark red berry-like capsule, 1 to 1.5 centimeters long.
Species Complex
Trillium erectum shares many anatomical details with other North American Trillium species. These species hybridize in the wild, which has led some researchers to group them into a species complex, specifically, a syngameon of semispecies. The combinations of traits that are supposed to differentiate members of the complex from one another are sometimes inconsistently combined in wild populations. This has led some researchers to declare the individual species invalid, and refer to the species complex collectively as T. erectum. Others acknowledge the existence of introgression and hybrid swarm formation between some or all complex members, but maintain that the named species within the complex represent convenient groups with common features. Members of the T. erectum complex have flowers with the following commonalities: petals that are coarse and stiff in texture, petals that do not change color after pollination, petals with prominent, netted veins, fleshy stigmas that are attached to the ovary separately, without a common style, and conspicuous, deeply-ridged ovaries. North American members of the T. erectum species complex:
T. cernuum
T. erectum
T. flexipes
T. rugelii
T. simile
T. sulcatum
T. vaseyi
The Asian species T. camschatcense, resembles the North American T. flexipes very closely, and itself has close relatives with similar floral features. However, trillium speciation in this group of Asian species is characterized by differences in chromosome number, with hybrids more definitively distinguishable from parent species by karyotype.
T. erectum var. album has white petals. All other petal colors constitute the nominate variety. Variety album occurs occasionally throughout the range of the species. At elevations less than in western North Carolina and other areas surrounding the Great Smoky Mountains, the white-flowered variety of T. erectum predominates.
The root was traditionally used as an aid in childbirth, hence the name "Beth root". Native Americans used root tea for menstrual disorders, to induce childbirth, and to aid in labor. The leaves contain calcium oxalate crystals and crystal raphide, and should not be consumed by humans.