A genus of 250-1000 species, herbs, primarily temperate. Hieracium is a complicated genus, with many apomictic races sometimes recognized as taxa. Often separated into Hieracium and Pilosella, an approach increasingly supported by molecular and morphological evidence, and has become the dominant approach in Europe and worldwide (Funk et al. 2009; Kilian, Gemeinholzer, & Lack 2009; Bräutigam & Greuter 2007).
ID notes:Many of our species hybridize, and some of the species listed above are apparently hybrid derivatives. I prefer to treat taxa such as H. marianum as species (even if hybridization-derived) because they regularly occur independently of the parental taxa. Other hybrids of native species known in our area include: H. gronovii × paniculatum [H. ×alleghaniense Britton (pro sp.)], H. gronovii × venosum, H. paniculatum × scabrum, H. paniculatum × venosum [H. ×scribneri Small (pro sp.); H. scribneri – K1], H. scabrum × venosum.
Ref: Bräutigam & Greuter (2007); Cronquist (1980); Funk et al. (2009); Kilian, Gemeinholzer, & Lack (2009); Strother (2006t) In Flora of North America Editorial Committee (2006a). Show full citations.