The extremely poisonous hemlock plant has long been known for its deadly effects. It was used to execute the Greek philosopher Socrates in 399 B.C. and was written about in William Shakespeare’s 1606 “Macbeth,” (Act 4, scene 1, line 25), where three witches brew a potion with the highly poisonous plant.
That same toxic plant is making its way across the U.S. to parks, pastures and backyard gardens. The poison hemlock (or Conium maculatum) was initially brought to the U.S. from Europe as a garden plant, due to its attractive flowers. Hemlock commonly grows in the early spring, but in some locations can grow year-round as a perennial. Here’s a visual guide to how to identify this invasive plant:
Poison hemlock is a biennial, meaning it takes two years to complete its biological life cycle. The plant is hard to identify during its first year. All parts of the plant are toxic to humans and animals.
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The highly poisonous plant is found in almost every state, according to the National Park Service. “It’s everywhere. You about can’t drive U.S. 30 and not see it,” according to Jason Hartschuh of Ohio State University Extension. “It keeps spreading by wildlife and by water and flood plains.” The Center for Invasive Species and Ecosystem Health at the University of Georgia has documented the species making its way in counties across the U.S.:
The plant can quickly infest an area, preferring low-lying land such as marshes and fields with moist soils. Each plant produces seeds — up to 30,000 — that ripen between late June and August after it flowers. It’s related to the carrot family and resembles wild parsnip and water hemlock.
The plant is the most dangerous plant in the U.S., and every part is toxic to humans and animals. The roots of Queen Anne’s lace (also known as wild carrot) can be eaten raw or cooked. Hemlock looks similar, and can be easily misidentified. If ingested, symptoms can appear in 30 minutes to a few hours.
If you plan to remove the plant yourself, be sure to wear protective gear – such as goggles, face mask, gloves and a long sleeve shirt – before handling the plant. Don’t touch your face while working with the plant. Face masks can help minimize inhalation of particles. Your hands and clothing should be thoroughly washed afterward.
Herbicides can be used on the plant in the early spring, before the plant flowers. Any time after will be too late due to the risk of spreading seeds that could create more plants.
Digging and careful removal is the best option for plants near your home. It’s best to remove the plant before it blooms, taking care to remove the entire long taproot. Weedwackers and mowers can spread seeds and dangerous particles. The plant should be disposed of responsibly, since it can remain poisonous even after it has dried. The area were the plant was removed should be monitored for future growth.
Repeated rotary mowing can be effective in agricultural situations, when you want to get larger populations to stop growing on land where it can harm animals. Reseed with desirable plants that will compete with the hemlock.
PHOTOS U.S. Department of Agriculture; Contributing: Sarah Bowman and London Gibson, Indianapolis Star; Zach Tuggle, Mansfield News Journal
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