Scattered throughout most of the U.S. and Canada. Seeds that mature early in a season typically produce biennial plants. Seeds maturing late in a season often produce annual plants. Newly matured seeds germinate without light. Seeds that become dormant germinate best when exposed to light.
Biennial seedlings require a cold moist period to induce stem elongation and flowering.
In colder, more northern regions the proportion of annual plants is higher than in more southern clines. Prevent seed production by cultivation, hand pulling, or mowing plants. Plants with mature fruits can be burned to kill seed. Black henbane is unlikely to be confused with other species in the nightshade family because of its distinctive flowers and fruits. Both species may be very toxic to humans and animals, although grazing animals will not consume black henbane, unless other forage is unavailable.