Poison Hemlock, (Conium maculatum) has been located in multiple areas in Orange County: on Highway 70 between Efland and Hillsborough, vicinity of Lloyd Farm, Highway 70A between Churton Road and Highway 86 South, Miller Road, Governor Burke Road, and in the vicinity of Squires Road.
Conium maculatum has multiple common names such as California Fern, Deadly Hemlock, Nebraska Fern, Poison Fool's Parsley, Poison Hemlock, Poison Parsley, Spotted Hemlock, Winter Fern.
Poison Hemlock (Conium maculatum) is highly toxic and may be fatal to humans if eaten. It is a group 2 toxin, which is dangerous but rarely eaten because it is not palatable and has a bad odor. All parts of the plant are poisonous, with the mature plant and seeds/fruit being more toxic than other parts.
The toxin is called Lambda-coniceine (early growth) Coniine, and N-Methyl coniine, conhydrine and pseudoconhydrine. It can cause salivation, vomiting, diarrhea, muscular weakness, paralysis, nervousness, trembling, dilation of pupils, weak pulse, convulsions, coma, and death. The toxic alkaloids can cause dermatitis through handling.
Water Hemlock is a bi-annual herb with short tuberous roots and purple-striped or mottled, hollow stems with cross-partitions at the nodes and many of these at the base of the stem. The leaves look fernlike, similar to carrot leaves. It can be found in wet meadows, thickets, fresh water swamps, roadside ditches, floodplains, forest or natural area in wet areas, ponds, streams, or ditch banks.
In its first year, it will be in the form of a low-growing rosette. Maturing in the second year, it will develop a tall stalk, growing to up to nine feet. In ideal planting conditions, the plant can act as a perennial.
The tiny flowers are small, white, and form in umbrella-like clusters. They bloom from spring to fall, attracting a variety of bee, wasp and butterfly species. It is a host plant for the Black swallowtail butterfly. Although all parts of the plant are highly toxic, water birds do eat the fruits without effect.
There are look-alike plants that are similar to the white, umbrella head of poison hemlock, such as Queen Anne’s Lace and Elderberry.
If found, please take a photo of the plant and text it to Mart Bumgarner at (804) 318-7493. Include the location of the plant, your name and contact number. Bumgarner will map locations of the poison hemlock within the county.
Poison Hemlock can be controlled using a broad spectrum herbicide like glyphosate or a selective broadleaf herbicide like 2,4-D and dicamba. Once killed, the plant should be burned to prevent it from getting into the landfill or composted (which will spread the seeds).
Please email mart_bumgarner@ncsu.edu. with questions. Add subject line: “Poison Hemlock” to the email.