This monotypic genus is a weed of damp seepy acid soils, and it has become locally abundant in Appalachian regions of North America, especially at the base of road cuts through shales. It spread south from northeastern states; the first coll. from Ky. is dated 1978 (from HARL at NKY); most Ky. records have come from the work of R. Thompson (BEREA). The species remains virtually absent within the Bluegrass Region; the single coll. from FRAN (AP) was made in 1979; a coll. from JEFF (BE) was taken from cultivation and not mapped here. The related species, Petasites frigidus (L.) Fries, was erroneously reported from Ky. by BA (M). There has been much traditional European use of Tussilago in medicine, especially to relieve asthma and cough, or even for food, especially during starvation (e.g. Redzić & Ferrier 2010). However, plants often contain toxic quantities of the carcinogenic pyrrolizidine alkaloids, senecionine and senkirkine (Roeder et al. 2015). Selections have been made to reduce toxicity in herbal uses (Wawrosch et al. 2000).