Which Parts of Poison Hemlock Are Toxic?
All parts of the poison hemlockleaves, flowers, seeds, stems, and rootsare highly toxic.
Merely touching it or brushing up against accidentally causes severe, long-lasting injury.
The Spruce / K. Dave
How to Identify Poison Hemlock
The plant changes in appearance during its two-year life cycle.
Every stage of the plant’s life has clear identification markers.
The dark green leaves are alternate, mostly triangular, lacy, and deeply divided.
The Spruce / K. Dave
The leaves and stems are hairless.
The stem is sturdy yet hollow.
It might appear ridged because of its veins.
The Spruce / K. Dave
A telltale characteristic of the plant is the purple blotches or spots on the stem.
The leaves on the upper part of the stem are not as large as the basal leaves.
The bloom time of poison hemlock varies greatly from year to year depending on weather conditions.
Closeup of a poison hemlock flowerThe Spruce / K. Dave
The clusters are 2 to 3 inches in diameter and each flower consists of five small petals.
After the plant sets seeds, it dies.
The stems with the seed capsules, each containing two round and ribbed seeds, remain on the plant.
Closeup of Queen Anne’s lace flowersThe Spruce / Evgeniya Vlasova
The seed capsule splits and releases the seed when mature.
Most of them, however, have distinct features that set them apart.
While it prefers moist soil, it is otherwise not finicky about its location.
Also called a pioneer species, it quickly populates disturbed sites such as cleared woodlands.
It grows along roadsides, along farm fields, in ditches, marshes, and meadows.
Wear protective clothing (long sleeves) and avoid letting any skin touch the plant.
Wear protective gear when you do that and dispose of the seed heads in the garbage.
The fastest way to eliminate poison hemlock depends on the scope of the infestation.
If there are only a few small plants, pulling them manually is the quickest route.
Household vinegar and even the stronger herbicidal vinegar (acetic acid) will not kill poison hemlock.
Vinegar is not a systemic herbicide, so it does not kill the roots.
U.S. Department of Agriculture Agricultural Research Service.
Poison Hemlock.Invasive Plant Atlas of the United States.
University of Maryland Extension.
The Ohio State University.
Toxic Plants.University of California.
Wisconsin Department of Natural Resources.
Poison Hemlock Fact Sheet.
Jefferson County Noxious Weed Control Board.
Poison Hemlock.Thurston County Noxious Weeds Fact Sheet.
Control Options for Poison Hemlock.
Whatcom County Noxious Weed Board.
