Foxglove, castor beans, peacock flower trees and opium poppies are among 200 toxic flora Amy Stewart investigates in her book, . Stewart says she didn't write her book to scare people away from the outdoors, but to help them better understand nature and be aware of what she calls "horticultural villains."
Many of what Stewart calls "wicked plants" have a peaceful and stunning beauty. But she warns us not to be deceived. These are trees that blind, weeds that blister, shrubs that sting and bulbs that kill.
"I decided to define 'wicked' kind of broadly," Stewart says. "So, of course, it includes plants that are poisonous, plants that are very deadly, also plants that are painful. I also included plants that catch on fire, plants that smell terrible and all kinds of plants that are illegal or immoral in some way."
Some of these botanical villains, she adds, are aggressive and a bit violent.
"They wait for a really hot day or they wait until their seed pods are fully, fully ripe and actually burst open and can scatter seeds for hundreds of yards and even miles," she says. "One interesting example of that is the Gorse plant. You don't want to be in the way when it happens. Another neat one is something called the squirting cucumber, which is a cucumber, but not one you would want to eat. The fruit will actually explode when they get ripe. They scatter this slimy stuff for 20 feet around them."
Other plants, like the castor bean, are beautiful but deadly.
"If you live in a place where you have a hot summer, then castor bean is very dramatic annual plant to plant in your garden, but the seeds contain ricin, which is a very deadly poison," she says. "I think a lot of people are growing it without fully realizing how very toxic it is. But just a few seeds, if they're chewed well, could kill a person. In fact, it was something that the KGB used to assassinate communist defectors."
Another deadly plant is the strychnine tree.
"Strychnine is a poison. It's used in rat poisons. It's actually the seeds of a 50-foot [15-meter] tall tropical tree," she says. "One of the stories that I managed to dig up is a physician in the 19th century who was a serial killer. He actually murdered his patients, and strychnine was his weapon. Now, he was actually caught, convicted of his crimes and hanged."
She also warns against what she calls the most wicked plant - tobacco.
"Tobacco has killed more people than any other plant I could find," she says. "I mean, 90 million people have died because of tobacco."
Stewart says some of the wicked plants she profiles in her book are available in public parks and even spilling out of window boxes, while others are rare and hard to find. She says every continent except Antarctica has at least one: mandrake in Europe, death camas in North America, coca in South America, betel nut in Asia, iboga in Africa, and finger cherry in Australia.
But the poisonous properties of these plants, Stewart says, are how they defend themselves and survive.
"A lot of plants have defense mechanisms, certainly to protect them from predators. And, in fact, all of these poisons serve some purpose other than just to harm us."
And, she notes, wicked plants are not all evil. Many of them can be used as treatments for illnesses.
"The thing about all medicine is that a little bit can cure you, and a lot of it can kill you," she says. "I think that's true about a lot of plants. For instance, foxglove [which can be fatal if eaten] is a beautiful flowering annual or perennial, depending on where you live. It is also heart medication. There are examples in the book of plants where one poisonous plant can actually be used as a treatment for poisoning by another plant. In other words, one of them slows down your heart and the other one would speed it up again, or something like that."
Stewart says she hopes her book will help readers better understand plants, so they can protect their families and pets from the harm plants can cause.