This tall toxic biennial weed is widely naturalized across temperate regions of North America, but it is only common on moist fertile soils. It was first reported from Ky. in 1914 (Gm), when it had already "spread over much or all of the best agricultural sections, and... likely to be found by roadsides and pastures anywhere in Kentucky." It was concentrated in the Bluegrass region initially but become much more widely abundant after 1980, especially along major roads. Attempted control with herbicides in May-June is often too late to prevent seeding, and may actually reduce competitive pressure on its seedlings in the fall (especially where crown-vetch is killed). It is highly toxic to vertebrates and some insects (Vetter 2004); even handling the plant can cause problems in humans. The plant is a nitrophile, and its toxicity is largely attributed to somewhat volatile piperidine alkaloids (coniine and allies) that shut down mammalian nervous systems, including the heart, as first detailed by Socrates (Brickhouse & Smith 2002, Radulović et al. 2012, Hotti & Rischer 2017). Alkaloids are generally sbsent in Apiaceae. The mottled reddish lower stems of Conium maculatum (as in Cicuta maculata) may be a warning to herbivores (aposematic), but there appears to have been no testing of this hypothesis (Lev -Yadun 2009).