Weed of the Week: poison hemlock

Poison hemlock is a weed class B native to Europe, Asia and Northern Africa. This weed is toxic to humans and livestock. Other common names for this weed are carrot-fern, fool’s parsley, and spotted hemlock.

The entire plant is toxic to animals and humans, containing the poisonous alkaloid coniine and other alkaloids. Poison hemlock can quickly infest large areas of pasture as well as open waste places.

Poison hemlock is a very tall biennial plant that can grow up to 12 feet in height. It grows into a rosette the first year; a cluster of leaves growing on the ground and then flowering stems the next year. The flowers are small and white and occur in 4- to 8-inch umbrella shaped clusters. The leaves are fern-like, toothed, finely divided and have a strong odor when crushed. The stems are hollow, hairless and have noticeable purple blotches.

Poison hemlock prefers rich, moist soil, but is highly adaptable to other conditions. This weed reproduces by seed. Always wear gloves and protective clothing if working with poison hemlock as all parts of this plant are toxic. Do not burn plants due to the toxins within plant parts. Also, due to the plant’s toxicity, do not allow animals to graze live or dead poison hemlock plants.

If you have questions about poison hemlock or any other noxious weeds and their identification and control, we can help. Please contact Andy Lea at 360-795-3852.