This winter annual is widespread across temperate North America. There may be historical evidence and archaeological evidence (e.g. Henderson 1998) that this species is native in North America, not just Eurasia (Defelice 2002).. Gray (1864; see also F) noted: "Shaded ground, throughout the continent; probably as an introduced plant eastward." In Ky., it was first recorded early after settlement by Rafinesque and others (McMurtrie 1819), but it has generally been considered alien (Gm). Cr noted variation in chromosome number, from plants with relatively large seeds and long leaves (2n = 44 to 88 usually), to more depauperate plants (with 2n = 20 usually) that are potentially segregated as var. echinospermum (Wallr.) Farw. However, there does not appear to have been a comprehensive study of variation within this potentially annoying or useful species. Its diverse medicinal and nutrional uses have been documented in Eurasia (Defelice 2002); there are even some obscure suggestions of caffeine in the seeds (e.g. Fernald et al. 1958, Hanganu et al. 2018). Caffeine is a methylxanthine alkaloid known only from about 60 species in Malvaceae (Cola, Theobroma), Sapindaceae (Paullinia), Rutaceae (Citrus), Theaceae (Camellia), Rubiacae (Coffea) and Aquifoliaceae (Ilex); see Huang et al. (2016), Negrin et al. (2019), etc. Galium may be the only genus with caffeine in cool-temperate zones, but this needs confirmation.