Anyone who gardens for long enough or likes to spend a lot of time in the great outdoors will encounter plants that can cause itchiness or even pain, but there are certain plants that they should be especially wary of — wicked plants. In this week’s encore, New York Times bestselling author Amy Stewart joins me to discuss the stories surrounding the world’s most notorious plants.
Amy of Portland, Oregon, is the author of several nonfiction books about the natural world, including “Wicked Bugs,” “Gilding the Lily,” “The Drunken Botanist” and the subject of this conversation, “Wicked Plants: The Weed That Killed Lincoln’s Mother and Other Botanical Atrocities.” The latter features nearly 40 plants with sordid histories.
Amy Stewart is the New York Times bestselling author of several books about the natural world. Photo Credit: Terrence McNally
“If something’s green and growing in the ground, we tend to think that it’s for us and that it’s all organic and it’s plant-based, and it’s all natural. And we’ll just pop it in our mouths — and that’s a terrible idea,” Amy says. “The plant kingdom makes some of the most deadly poisons in the world.”
Instead of writing a guide to poisonous plants — there are several books like that already — Amy wanted to write about wicked plants’ intriguing stories.
“I didn’t care that it could kill somebody,” she says. “I just wanted to know who it had killed, and so it ends up being this quirky little weird book that’s not at all comprehensive, but that’s purely entertaining.”
She wanted to write stories that no one knew about, stories that couldn’t be found in the Wikipedia entries about these plants. “Where can I go outside of the plant world to find stories about these plants?” she wondered.
Amy looked through 200-year-old medical journals and read obituary archives to uncover stories that had been lost to history.
Read on for a condensed version of my conversation with Amy, or you can see the show notes from the original airing for the unabridged version.
Chemical Factories
The Chelsea Physic Garden is a botanical garden in London founded in 1673 by the Worshipful Society of Apothecaries to grow medicinal plants. I visited for the first time a couple of years ago, just after the Chelsea Flower Show. I would have appreciated it even more had I already read “Wicked Plants.”
Amy describes plants as living green chemical factories that produce compounds for their own survival. “They’re not thinking about us. They’re doing it for themselves,” she says. Some of those chemicals deter predators or attract pollinators, and “some of those chemicals happen to be really useful as medicines,” she explains — though only in the right dose. “There’s a very thin line between medicine and poison.”
Hundreds of years ago, Londoners turned to apothecaries when they were sick, and plants were all they had. Remedies were often dried or soaked in alcohol to extract and preserve their chemicals. “You had these pharmacists who were just handing out plants to people and hoping that would work, and usually it didn’t,” Amy says. Still, when plants did work, it was important to keep them close at hand.
The Chelsea Physic Garden in London, England. Photo Credit: Joe Lamp’l
“The Chelsea Physic Garden was a place where those plants could be grown and where pharmacists could look at them and identify them,” Amy explains. At a time when books were rare, seeing a living plant was invaluable.
The garden also maintained poisonous plants so apothecaries would know which ones to avoid.
“The Chelsea Physic Garden is still there today, and all of those things still exist inside that garden,” Amy says. Visiting it feels like time travel — and it also inspires modern gratitude. “Thank you, Walgreens. I probably don’t say it often enough. Super glad you’re there.”
At the Chelsea Physic Garden, this cloche protects important plant specimens from the cold.
Photo Credit: Joe Lamp’l
Rosary Pea
Of all the plants in Amy’s book, the one that hits closest to home for me is the rosary pea (Abrus precatorius). This plant is very common in the tropics, and it is also found where I grew up, in Miami. The peas themselves are bright cherry red with black tips — very intriguing to a child. I can’t believe my mother didn’t go and hack every rosary pea down within a block. But I must have never eaten one because here I am today to talk about them.
“I love this one because I love what they look like,” Amy says. “They’re very satisfying little creatures. These seeds, they’re quite hard and round and smooth. And they kind of remind me of little ladybugs. They’re about the size and color of a ladybug with just one black spot.”
The toxin that comes from Abrus precatorius is called abrin, and it has been used in international terrorism incidents before. “It is known as one of the most toxic plants in the world in terms of how much it would take to kill a person,” Amy notes.
The peas are used for beads in jewelry-making.
“You punch a hole in it and run a string through it, and you can make a very charming necklace, but punching that hole in it makes it easier for the poison to get into your digestive system,” Amy says.
A rosary pea copper etching by Briony Morrow-Cribbs for the book “Wicked Plants” by Amy Stewart.
Castor Bean
The castor bean (Ricinus communis) is a gorgeous plant with dark red leaves and flower spikes. I see it every time I visit the Georgia Botanical Garden in Athens, Georgia, and I think to myself, “If people only knew.”
The beans contain ricin.
“Ricin got kind of famous in the ’70s when there was a Russian dissident named Georgi Markov who was assassinated by the KGB,” Amy says. “He was in London and after he died, at the hospital, they found a little pellet in his leg that contained ricin.”
The pellet was shot into his leg by a modified umbrella.
“You don’t have to run screaming away from [castor bean],” Amy says. “Just don’t eat it.”
The Brooklyn Botanic Garden hosted an exhibit about “Wicked Plants” when the book came out in 2009.
“They had a lot of castor bean, and they were telling me that after 9/11, the newly formed Department of Homeland Security came around wanting to see their castor beans and wanting to document where those plants were,” Amy recalls.
The Brooklyn Botanic Garden employees had to explain to DHS agents that castor bean is for sale at garden centers everywhere and can be bought from a seed catalog.
“It’s this disconnect between how the horticulture world works and how counterterrorism works,” Amy says.
Castor bean is an attractive plant but also the source of the poison ricin. (Credit: Copper etching by Briony Morrow-Cribbs)
Hemlock
Hemlock (Conium maculatum) is the plant that was used to kill Greek philosopher Socrates as capital punishment for impiety.
Hemlock is in the carrot family (Apiaceae) and looks similar to Queen Anne’s lace, though it has purple spots on the stems.
“After the book came out, I got a call from a guy who had been poisoned by hemlock, and it was so fascinating to me to get to talk to someone who’d been through it,” Amy shares.
He was growing carrots in his backyard, in the Pacific Northwest, and hemlock turned up as a weed among his carrots. He harvested some carrots to make kimchi, and he didn’t pause when some of the “carrots” he harvested came up white.
He ate a little kimchi and then got in his car to drive to a friend’s house. On the way, he noticed that his peripheral vision didn’t work. He could not move his eyes from side to side. That was the beginning of the paralysis that sets in with hemlock poison, Amy explains. It paralyzes from top to bottom.
“He was able to get right to an emergency room, but he also had the presence of mind to call a poison control center,” Amy says. “… So they were able to quickly troubleshoot, ask him the right questions, narrow it down, hit on this possibility, and they called ahead to the emergency room and said, ‘He’s coming. We suspect hemlock poisoning. Here’s what you want to look for. Here’s what you want to test for.’”
Hemlock is in the carrot family and looks similar to Queen Anne’s lace, only it has purple spots on the stems.
Photo Credit: Amy Prentice
Sago Palm
Sago palm (Cycas revoluta) is a cycad houseplant that can also be grown outdoors in warm climates.
“It’s very toxic to dogs, and unfortunately, after the book came out, I have heard from so many people whose dogs were poisoned by sago palm,” Amy says.
Plants don’t come with warning labels, so if you have a curious pet, research any plant before bringing it into your home or planting it in your yard.
Sago palm is a cycad houseplant that is very toxic to dogs. (Credit: Copper etching by Briony Morrow-Cribbs)
Lilies
The lilies (Lilium) growing in your garden or sitting in a vase indoors are highly toxic to cats. Exposure can cause kidney failure, and there is little that can be done to treat it, Amy says.
Oleander
Oleander (Nerium oleander) is a common Southern shrub or small tree that contains cardiac glycosides capable of stopping the heart. Its candy-colored red and pink flowers can be especially tempting to toddlers.
Oleander contains cardiac glycosides that can stop the heart. (Credit: Copper etching by Briony Morrow-Cribbs)
Jimsonweed
Jimsonweed (Datura stramonium) is a nightshade with trumpet-shaped flowers, also known as devil’s trumpet.
“You can buy them at the garden center. They’re beautiful in containers. I love them,” Amy says. But they can interfere with heart rate and breathing and cause a lot of dizziness. At high levels, the poison can cause hallucinations and kill.
“And one of the interesting things about Datura is you can get a little of the poison through your skin,” she noted.
If kids just roll around in jimsonwood, they can get poisoned. The symptoms to watch out for are a red and flushed face, babbling, not making any sense, and having trouble breathing.
Ergot
Ergot (Claviceps purpurea) is a fungus that grows on cereal crops like rye and other grains.
“Ergot contains precursors to LSD,” Amy says. “… You can get crazy and very unpleasant, frightening hallucinations from consuming rye grains that have been infested with ergot. And the really tricky thing about this is that it survives the process of being baked into bread or brewed into beer.”
As far back as the Middle Ages, there are records of outbreaks of ergot poisoning. “The whole village kind of goes crazy all at once,” Amy says.
Ergot can also explain the Salem witch trials. Girls went crazy all at once, and their behavior was attributed to them being bewitched.
“If you look back, it turns out that the conditions were right for ergot poisoning that year. It had been a very wet winter and so forth,” Amy says.
Rye infected with ergot. Ergot is a fungus that grows on cereal crops. (Credit: Copper etching by Briony Morrow-Cribbs)
Deadly Nightshade
The nightshade family (Solanaceae) includes familiar food crops such as tomatoes, peppers, and eggplants, as well as tobacco and deadly nightshade (Atropa belladonna).
Deadly nightshade is a low-growing herbaceous plant with small purple berries. Amy cites a medical journal article about an elderly woman who took daily walks and ate the berries she picked along the way. As she became increasingly delirious, her symptoms were blamed on age — until doctors noticed the pattern was seasonal. She was only ill in late summer and fall, when deadly nightshade was fruiting.
Deadly nightshade may look like an edible fruit but is poisonous. (Credit: Copper etching by Briony Morrow-Cribbs)
I hope you enjoyed my conversation with Amy Stewart on wicked plants. If you haven’t listened to the podcast yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
Have you had an encounter with any wicked plants? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
Episode 120: Poison Ivy: What You Need to Know to Minimize Its Impact on You and Your Landscape
Episode 382: The Tree Collectors: Amy Stewart’s Tales of Arboreal Obsessions
Episode 389: Wicked Plants: Mother Nature’s Dangerous Botanical Creations
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Amy Stewart on Instagram | @amystewart
Amy Stewart on X | @amy_stewart
“The Tree Collectors: Tales of Arboreal Obsession” by Amy Stewart
“The Drunken Botanist: The Plants that Create the World’s Great Drinks” by Amy Stewart
“Wicked Plants: The Weed That Killed Lincoln’s Mother and Other Botanical Atrocities” by Amy Stewart
“Wicked Bugs: The Louse That Conquered Napoleon’s Army & Other Diabolical Insects” by Amy Stewart
“Gilding the Lily” by Amy Stewart
“Flower Confidential: The Good, the Bad, and the Beautiful in the Business of Flowers” by Amy Stewart
“The Earth Moved: On the Remarkable Achievements of Earthworms” by Amy Stewart
“From the Ground Up: The Story of a First Garden” by Amy Stewart
“Taming the Garden” film trailer
Disclosure: As an Amazon Associate, I earn from qualifying purchases. I receive a commission every time you purchase a product through an Amazon affiliate link. Some product links in this guide are affiliate links. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast was based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Milorganite, Soil3, Territorial Seed Company, Cool Springs Press / Quarto Group and Dramm. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.
