Smooth coneflower inhabits rocky, gravelly, or sandy soils in locations such as roadside cuts and thin soil clearings that tend to suppress weeds and other heavy vegetation
Echinacea laevigata is an attractive coneflower native to the Piedmont, from Pennsylvania to Alabama. It’s habitat requirements are broadly similar to Echinacea purpurea, but is far less tolerant of heavy soils, cold wet winters, and vegetation encroachment. The U.S. Fish and Wildlife Service determined the species to be Endangered in 1992; read their submission here.
As with many plants carrying the ‘Endangered’ label, it is the plant’s preferred habitat that is endangered more than the plant itself. In fact, many of the easily-observable populations host a large number of plants that are performing quite robustly. In our experience, the primary factor limiting this species’ range is competition from other plant species, particularly invasives. Echinacea laevigata sets copious quantities of large, viable seed that germinate readily when treated with about 30 days of gentle conditioning. However, in our work with this species, we have noticed that the seed will rot if held too long in cold, moist conditions and that seedlings will not develop properly if grown in anything less than full-sun conditions. Most of smooth coneflower’s leaves are basal (at the base of the plant) making it particularly susceptible to larger and more robust plants such as Japanese barberry and Rubus species, which tend to invade sites hosting Echinacea laevigata, pushing them out.
Echinacea laevigata exhibits several morphological features consistent with shale or alvar barren species; thick rhizomes, thick glossy leaves, and most of its biomass growing close to the ground (to preserve moisture). Echinacea laevigata populations do not seem to also host Echinacea purpurea, which suggests some environmental constraint or mechanism that keeps them separated. Perhaps it is that the moist spring conditions that favor Echinacea purpurea germination also reduces Echinacea laevigata seed viability and the well-drained soils that Echinacea laevigata can withstand cannot also support Echinacea purpurea during hot summer droughts. The actual factors that push these two species into different habitats requires further study. The U.S. Fish and Wildlife Service has declined to describe the critical habitat requirements for this species.
Echinacea laevigata is not a particularly useful landscaping species due to producing just one flower per plant. Some plant breeders have experimented with using Echinacea laevigata to create Echinacea purpurea cultivars with improved survivability in thin or dry soils.
The most northerly historical populations were in Pennsylvania, in both Berks and Lancaster counties.; these populations are considered extirpated but we have not checked. More than 50 other known populations remain in Virginia, North Carolina, South Carolina, and Alabama.
USDA range map for Echinacea laevigata.