Crop and livestock producers with poison hemlock in their pastures, crops or ditches should consider treating the weed in the fall.  That's the advice of Purdue Extension weed specialist Bill Johnson.

Johnson says Poison hemlock is a biennial weed that is toxic to both livestock and humans, if enough is consumed. It can be identified by its finely divided, toothed leaves and white flowers. Its stems are hairless, have purple spots or blotches and can grow to 2-7 feet in height.

Johnsons says “The weed seems to be spreading, becoming a more common occurrence in pastures, agronomic crops, fencerows and roadsides and it can be difficult to control in the spring.”  The plant growth and appearance is more visible in the spring, when the plants “bolt” or elongate rapidly and the white flowers bloom, so that's when most people become concerned with it. But Johnson says there is active rosette formation of the weed in the fall and it's easier to control in the fall because it's more sensitive to herbicides.”

Purdue Weed Expert Bill Johnson