Conium maculatum (Poison Hemlock)
Natasha Shangold, City of Rockville nshangold@rockvillemd.gov
As we are in the midst of summer, many of us enjoy planting a garden full of fresh veggies and herbs for ourselves and perhaps pollinators, or some of us may even enjoy foraging around. To those who are familiar with the Apiaceae family, these plants contain carrots, parsley, dill, and many others but not all are edible. Enter Conium maculatum, also known as Poison Hemlock and commonly named this for good reason, is also part of the Apiaceae family, a biennial growing 6 to 10 feet in height with small white flowers in clusters along ditches, bordering pastures and croplands, and roadsides with a bad musty odor.
Originally from the Mediterranean region and native throughout northern Europe, western Asia, and northern Africa, it was thought to be the poison used against the Greek philosopher Socrates as it contains high concentrations of the chemical coniine, which paralyses the motor nerve endings of the skeletal muscles and depresses the autonomous nervous system, causing the toxic effects (Alliance for the Chesapeake Bay, 2019). Symptoms of poisoning include salivation, vision impairment, stomach pain, seizures, paralysis, coma, and if consumed at a high dosage, death (Alliance for the Chesapeake Bay, 2019). While it may appear similar to Queen Anne’s Lace, Poison Hemlock will have a smooth stem with purple splotches and lacy pale green leaves (Nibalia, 2018).
As Maryland continues to disturb land areas for new developments, Poison Hemlock will be able to thrive in these areas, especially those with adequate moisture and low elevations. Roadsides are the most problematic because as mowers cut the plant, they can spread the seeds even further around at far distances (Fitch, 2018). Additionally, as it can be poisonous to humans and livestock, it is best to remove as quickly as possible when detected.
When removing Poison Hemlock, whether by hand or mowing (though mowing is not recommended as mentioned before because it can spread plant material around) or applying herbicide, wear gloves, long pants, long sleeves, and a face mask. Also, once removal is complete, immediately take a shower as well as wash clothes separately from other laundry (Nibalia, 2018).
While we may have purple carrots, we should be skeptical when we see purple stems above ground. All in all, stick with what you know and love to plant but remember to continue to plant native Apiaceae plants to help our pollinators and provide a host plant to the Black Swallowtail butterfly.
References
Alliance for the Chesapeake Bay. (2019, August 8). Dangerous plants of the Chesapeake Bay watershed. https://www.allianceforthebay.org/2019/08/dangerous-plants/
Fitch, J. (2018, June 24). Poison hemlock spotted in area pastures, roadsides in Tri-State area. Herald Mail Media. https://www.heraldmailmedia.com/story/news/2018/06/24/poison-hemlock-spotted-in-area-pastures-roadsides-in-tri-state-area/116622512/
Nibalia, E. (2018, July 5). Garden Q&A: How to get rid of poison hemlock. The Baltimore Sun. https://www.baltimoresun.com/features/home/bs-re-garden-qa-0708-story.html