Poison hemlock is a biennial that reproduces by seed. Its growth trait allows it to germinate and form a rosette during the first year of growth. It will then bolt, set seed, and die the following year. All parts of this plant are poisonous. Mechanical, chemical, and/or biological methods can be effective in controlling this noxious weed.
Control Half the battle, in managing this weed, is to prevent it from seeding. The other half is tending to the existing seedbed already present in the soil.
This department has seen good results in rangeland, pastures, and other non-crop areas by applying products containing, chlorsulfuron, metsulfuron, or dicamba.
Poison hemlock can be destroyed by hand pulling, hoeing, tilling, or digging. It is seldom a problem in cultivated fields.
Competitive crops or introduction of desirable vegetation can be effective in controlling this poisonous plant. Establishing a cover crop will also choke out germinating weeds.
Biological control is often used in areas that are not disturbed and where accessibility is difficult. The larvae of the defoliating moth, Agonopterix alstroemeriana, will chew numerous holes in the leaves and flowers. Attacked plants are extensively defoliated and damaged.
When choosing any kind of control method, assure that your choice is suited for your particular situation. Always read and follow the entire product label before applying any herbicide.