Poison Hemlock Confirmed in Richland County

An area of poison hemlock has recently been confirmed in Richland County. This plant is toxic to livestock, wildlife, pets, and humans making proper identification and management important.

Poison hemlock is a deep tap rooted biennial that can grow from three to eight feet tall. This plant is in the parsley family and its roots have an odor similar to parsley and carrots. During its first year of growth, the plant forms a rosette and typically remains in the vegetative stage. During its second year, it produces a tall stem, with the lower portion of the stem having distinct purple spots. The leaves are triangular, highly dissected, and are pinnately compound, meaning that each leaf is made up of leaflets that sprout from each side of the leaf stalk. These leaflets are segmented and are 1/8 to 1/4 inch long. Poison hemlock typically flowers in July and August. The flowers are white with green petals at the base of the flower. The flowers are arranged in an umbrella-shaped bunch.

Poison hemlock can invade crops, yards, and grazing areas. All parts of the plant are toxic to animals and humans, with the lower stem and root being the deadliest. It is the largest threat to livestock in grazing areas. Because of its toxicity, careful management of poison hemlock is important. Both mechanical and chemical control options are available. If it is a small, isolated patch, digging up the plants and being sure to remove the crown and large taproot is one option. Make sure to wear gloves while doing this and dispose of the poison hemlock when complete. Chemical options for poison hemlock include products such as 2,4-D and glyphosate.

If you have any questions or need assistance with plant identification, please call the MSU Richland County Extension office at 406-433-1206.