This is a common "noxious" weed in temperate regions of North America. It has increased to become particularly successful along roadsides, ditches and other transitions from cropland to old fields and thickets, especially in farmland where no-till practices have been used (DiTomasso et al. 2009). The plants are toxic to mammals, and consumption is avoided. Its original habitats may have been largely along shores and in low meadows subject to intense browsing. In 1914, Gm just noted: "grows in tufts in clayey or gravelly soil in western Kentucky." Records mapped here include var. glaberrima A. DC. and var. pubescens (Mitchell ex R. Br.) Woods, which are not generally recognized in recent treatments. There are also a few records of hybrids with sibiricum or androsaemifolium; see notes under those names. There are reports of 2n =16 from all three taxa but some uncertainties remain, as reviewed by DiTomasso et al. (2009)..