This weedy southeastern winter annual (or perhaps biennial) may have been present in Ky. at the time of settlement. But after 1940, glabella seems to have increased greatly and spread in the Ohio Valley towards the north and east, especially in or near areas cleared and drained for corn and soybean fields. Short (1837) listed it under the name Senecio lobatus Pers. with this note: "seems to be abundant on the lower Mississippi, has been found by Mr. Griswold at Louisville; but we believe has not been seen higher on the Ohio." However, neither Gm nor B listed it. A similar trend is recorded in Ind., where it was known at New Albany in 1838 (across from JEFF in Ky.), but virtually unknown before 1900; then it spread over the southern third of the state during 1900-1940 (D). In Ohio glabella was almost unknown before 1990, but it has now been classified as a noxious alien weed. It is considered "adventive" in Mich., Pa. and W.Va. (K); it remains unknown in Va. (W).. P. glabella is now a locally abundant weed in most regions of Ky. especially on lowlands and damp uplands where there is "no-till" farming but also sometimes in overgrazed pastures. In such fields, it completes its life-cycle in winter to spring, flowering mostly in April. But flowering can also occur as late as June in less disturbed areas. The hollow, striated stems are distinctive (FNA 20).The plant is toxic to mammals, probably due to pyrrolizidine alkaloids (Knight & Walter 2001, Roemer et al. 2015).