Trillium erectum

Flora of North America (2002) recognizes two varieties: Trillium erectum var. album and T. erectum var. erectum but Kartesz (1994) and Weakley (2015) do not. While the recognition of the varieties differs between these treatments, the full species concept in Flora of North America is equivalent to those of Kartesz and Weakley.

Trillium erectum is a slow-growing species that occurs in eastern Canada and the eastern U.S. at middle to high elevations in moist woods and on wooded slopes. It is relatively common throughout the central portion of the range. This species has multiple low level threats including deer browse and forest acidification. This species is commercially traded as a medicinal plant.It is also harvested for ornamental uses but the severity and scope of this threat are not known.

Trillium erectum occurs across eastern North America, from Nova Scotia, New Brunswick, and the Gaspé Peninsula south and west to southeastern Ontario and south through New England and the Great Lakes Region to Indiana, Michigan, Ohio, Delaware and further south through the Appalachians, as far south as high elevations of Georgia, South Carolina, and Tennessee. It is also found on both the Upper Peninsulas of Michigan and the southwestern corner of the state (Case and Case 1997). Distribution in Illinois needs to be confirmed.

Trillium erectum is widespread in Michigan, although its abundance throughout the state varies from uncommon to frequent (F. Case, pers. comm., Jan 2001). This species is reportedly rare in Illinois, Rhode Island and Delaware, although its nativity in Illinois should be investigated. It is common throughout moist woods in Pennsylvania (Rhoads and Block 2000) and throughout mountainous regions of North Carolina, South Carolina Virginia, and West Virginia. It is also common at the northern reaches of its range in New Brunswick, Ontario, and Quebec.

Like other Trillium, this species is impacted by invasive species and deer browse, especially as the surrounding land is developed and fragmented, increasing exposure to these threats. Areas with high concentrations of deer tend to have higher rates of herbivory, with some Trillium species, like Trillium grandiflorum, being described as a favorite food source and other species as a less favored food but still at risk of browse. However, the amount of herbivory by deer is also variable from year to year and by site depending on many environmental and landscape factors (Knight 2003). Deer appear to prefer larger flowering specimens and consecutive years of heavy deer browse reduces reproduction, partly by causing a regression to non-flowering single leaf plants: this leads to population declines, or potentially local extirpations (Augustine and Frelich 1998; Knight 2003; Rooney and Gross 2003; Webster et al. 2014). However, deer have been documented to disperse seeds of T. grandiflorum, providing a long-distance dispersal mechanism where ants are the normal mode of dispersal (Vellend et al. 2003). Populations should be monitored to assess potential decline due to deer browsing. In the south, Feral hogs (Sus scrofa) are known to dig plants and disturb plants.

For some species, a lesser understood threat may be the acidification of forest soils through acid deposition (Thompson and Sharpe 2005).

This species is also commercially available for medicinal use. Some experts in the medicinal plant industry have suggested that trade is medium to large and demand has increased over the past ten years (Robbins 1999). Therefore, future market trends and potential pressures on wild populations should be monitored. Reported pressures on wild populations due to picking and digging for ornamental uses may be exacerbated by its relatively slow maturation (pers. comm. A. Bentley, December 2000).