Erigeron sionis var. trilobatus
Rhodora 95: 398. 1993.
Basal leaves: blades (2–) 3–5 (–11) mm wide, margins usually entire or dentate, rarely deeply lobed. Ray corollas drying pink to dark blue. 2n = 18.
Phenology: Flowering Jul–Sep.
Habitat: Limestone cliff bases and faces, crevices, ledges, shelves, soil accumulations, talus, limestone gravel, lakeshores, bristlecone pine, spruce-fir-aspen, aspen, limber pine, Engelmann spruce
Elevation: 2200–3100 m
Of conservation concern.
The leaves of var. sionis tend to be narrower and more deeply lobed than those of var. trilobatus; morphologic intermediacy makes these plants hard to separate even at varietal rank. Differences in habitat and an essentially allopatric distribution, however, suggest that two evolutionary entities are present.