Here's Why You Should Stay Away from Poison Hemlock

Poison hemlock is an invasive plant that grows everywhere in the U.S.. First brought here as an ornamental in the 1800s, poison hemlock (Conium maculatum) is dangerous because even a small amount, if ingested, can be deadly.

Native to Europe, northern Africa and western Asia, it was used in ancient Greece to execute political prisoners. The most famous victim was the philosopher Socrates.

All parts of this plant (leaves, stem, fruit, and root) are toxic when eaten.

Skin irritation also is possible upon contact with the plant.

"Poison hemlock contains alkaloids which cause respiratory distress if ingested," says Pamela Bennett, associate professor and master gardener program director at Ohio State University. "It's a huge problem for livestock, such as sheep and cows, who may graze it in a pasture. A small amount is fatal for livestock."

This plant is a biennial, meaning it takes two years to mature. The first year it grows in a rosette shape, low to the ground, making it difficult to notice.

"But people notice it the second year because it shoots up a stalk 8 or more feet tall, producing white umbrella-shaped flowers and numerous seeds, so it keeps coming back and spreading," says Bennett.

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