This is a widespread species in eastern and central North America, with much variation; reported 2n = 32, 34, 36 (Cr). In addition of native variants, there are many cultivars, some of which appear to result from hybridization with other species (incuding serotina, media and perhaps Mexican taxa). Further examination of colls. in Ky. is desirable for more reliable separation of varieties. Var. fistulosa is thinly or densely pubescent, including long spreading hairs on leaf surfaces (especially the lower), and on stems in the inflorescence (see also W). It appears concentrated in hilly regions from midwestern to Appalachian regions. In var. mollis, this pubescence is usually denser, with shorter appressed hairs predominating. Var. mollis also tends to have larger flowering heads and narrower leaves with deeper bluish-green color and sharper flavor, yet more susceptibility to powdery mildew. Var. mollis is more widespread and generally more abundant, especially on base-rich soils. In Ky. the two taxa are sometimes mixed in the same locality, but appear generally distinct, with var. fistulosa sometimes flowering 1-3 weeks later.