The lethal Cicuta maculata. Michel Foret/ Alamy

Within the expansive Apiaceae family are some of the tastiest and most versatile food plants in the world: carrot, celery, cumin, dill, fennel, parsley, anise, parsnip, coriander. There is perhaps no other family of plants that enable you to make an entire dish, with contrasting flavors and textures, without straying from its boundaries. (Roast some carrots with cumin and coriander and top it with chopped cilantro!)

But every family has at least one bad egg. And Apiaceae, as one of the best families, has, by many accounts, the worst egg in all of North America. This plant hides in plain sight, widespread throughout the country, with pretty flowers and a similar appearance to its relatives. Do not be fooled. This is the most violently toxic plant on the continent. This is the spotted water hemlock.

Spotted water hemlock grows in freshwater marshy or swampy areas throughout the entire continent of North America, save the island of Newfoundland. It can be found in Alaska and Florida, in the vast unpopulated stretches of the American west and in the parks of New York City. It is not especially common, but its range is massive.

Typically growing a few feet tall, the spotted water hemlock has pretty, umbrella-shaped arrays of tiny white flowers. It is a bushy, weedy-looking plant, the kind where you can’t tell exactly how many individual plants make up a dense patch. Its stems are distinctive, with purple splotches on them, and all meeting in a bulbous swelling near the ground.

There are many plants that look quite a bit like the spotted water hemlock, and which are far friendlier. Its flowers are very similar to those of Queen Anne’s lace. Its roots and stem look, aside from the purple coloring, much like wild parsnip. There’s also the smell element; the scent of a plant can tell you a lot about what it is. Wild garlic looks mostly like grass, but break a leaf, and bam, you’ll smell a strong onion-garlic flavor, and know you’re holding something edible. Spotted water hemlock, when cut, emits a strong parsley-carrot odor.

Please do not eat the spotted water hemlock.

An illustration of spotted water hemlock, from Farm Weeds of Canada, 1906. Internet Archive/ Public Domain

There are toxic plants that may kill you but will be nice about it. “Poison hemlock is much better,” says “Wildman” Steve Brill, a New York based foraging expert and tour guide with an encyclopedic knowledge of the edible and not-so-edible plants of the Northeast. “You just stop breathing and your heart stops.” Socrates, when choosing death over a life in exile as an old man, chose poisoning by poison hemlock. It was a gentle death.

Poison hemlock is related to spotted water hemlock, but, um, only taxonomically, not in the way its poisons affect mammals. Here is Brill’s explanation of what happens when you eat spotted water hemlock:

Every single muscle starts firing and contracting, so you have convulsions, you chew your tongue into ribbons, you vomit but then you can’t open your mouth because the jaw muscles are contracting 10 or 20 times as hard as they normally do, and you die a horrible death.

Here’s another description of the effects, from a member of the Seneca American Indian community, written in a book on Iroquois suicide rites from 1941:

There is nothing good about the plant. Those who eat it will die in two hours. It must be a painful death. It twists the arms and ankles and turns the head back. Finally they die in a last wretching convulsion. They say it turns the eyes back.

There are many reports of the spotted water hemlock’s use as a suicide tool among the Iroquois nation; the most commonly cited occasion is upon the discovery of marital infidelity. There are plenty of other ways to take your own life; the spotted water hemlock is specifically chosen because it causes the most horrible, painful death possible.

A detail of spotted water hemlock, sighted along the Red Butte Creek in Salt Lake City, Utah. Andrey Zharkikh/ CC BY 2.0

The primary toxin in the spotted water hemlock is called cicutoxin, which works on the nervous system as an incredibly potent stimulant. Humans, and other mammals, have a neurotransmitter called “gamma-aminobutyric acid,” which is usually cheerfully abbreviated to GABA. GABA is an inhibitory neurotransmitter, which means it functions basically—apologies to neuroscientists for all of this simplification—like an emergency brake on a car. It serves as a balancing force, stopping stimulants from running rampant and telling your brain to press all the buttons that control your body.

Cicutoxin is a GABA antagonist; it turns off the brakes. Without that GABA emergency brake, the brain goes nuts: everything starts firing. Anyone unfortunate enough to ingest cicutoxin starts sweating, vomiting, and salivating violently. Kidney failure is common, as is an irregular heartbeat and difficulty breathing. Muscles start contracting so hard they can dislocate bones.

“It’s the deadliest plant in North America, deadlier ounce by ounce than any mushroom,” says Brill. “One bite can kill you.” Studies back that up; even the smallest dose can result in death. In fact, scientists don’t even really know what the minimum dose is to kill a human, or if there even is a minimum dose. It seems possible that ingestion of any quantity of spotted water hemlock whatsoever can be enough to trigger those extremely unpleasant effects.

All parts of the spotted water hemlock contain cicutoxin, but it’s most concentrated in the plant’s roots. This is extremely rude, because those roots look a lot like wild parsnip, smell a lot like wild parsnip, and, perversely, seem to actually taste good. There are several reports over the centuries of people eating spotted water hemlock and reporting that it has a sweet and pleasant flavor not unlike a wild carrot.

Cicuta maculata at the Kickapoo Valley Reserve, Wisconsin. Joshua Mayer/ CC BY-SA 2.0

While even tiny amounts of spotted water hemlock can be deadly, consumption does not always result in death. Nobody knows why, but sometimes people survive; with immediate dosing of various barbiturates and benzodiazepines, basically drugs that try to get GABA back on its feet. Sometimes this works. Sometimes it doesn’t. There are reports of people dying from eating spotted water hemlock throughout the 20th century, and there was even a case of spotted water hemlock poisoning published in an article last year. (The patients in that one survived, luckily.)

Animals are not usually so lucky. Brill says he has never seen a wild animal eating spotted water hemlock; “I would presume the toxins are to stop animals from eating it, and I don’t see holes in the leaves,” he says. Some birds do eat it; birds are not generally subject to the same toxins that mammals are, and can eat plants that would kill a mammal (and vice versa).

But it is most often eaten by livestock, earning it one of its names: spotted cowbane. Cattle have been known to dig up the plant and eat its roots, which is just as dangerous to them as it is to us.

From the Apiaceae family, from top left: celery leaves; wild carrot; root parsley; sea holly; fennel flowers. RoRo/ CC BY-SA 3.0

Brill noted that identifying the spotted water hemlock is not hard; the purple blotches, the bulbous stem, and the fact that it grows in marshy mud are all dead giveaways that this plant is not some lovely wild carrot or parsnip. But the spotted water hemlock continues to poison North Americans, an absurdly, violently deadly plant in a family of delicious relatives.