This tetraploid (2n = 48) is widespread across eastern North America except for the southeastern Coastal Plain. It is locally abundant in strictly mesic woods, but generally absent from areas that have been cleared or intensively farmed in the past. It is likely that past rooting by free-ranging pigs has greatly reduced species of this genus. E. americanum may have originated from crossing of rostratum and umbilicatum (FNA 26), variation may reflect this parentage. Flowering dates vary much across the state, mostly from late Mar to late Apr. In FAYE, Short (1828-29) stated "blooms about the 20th of March"; and this date remains a reliable average estimate for c. Ky. Despite the warmer climate of recent decades, there does not seem to have been a distinct shift in flowering dates for this species in Ky. Herbarium collections from W.Va. indicate a shift of about one week earlier in average flowering date during the past 10 decades; but this trend was largely due to decrease of late fllowering rather than increase in early flowering (Petrauski et al. 2019)