Over millions of years, plants have developed some crafty ways to fend off hungry animals. Deadly neurotoxins, thorns capable of puncturing car tires, and powerful digestive enzymes are just a few. Following the recent discovery of Nepenthes attenboroughii, a giant pitcher plant large enough to digest rodents, PM tracked down poison-plant aficionado Amy Stewart to discuss some of the world's deadliest plants. Stewart, who is the author of Wicked Plants: A Book of Botanical Atrocities, lives in Eureka, where she tends a garden that contains more than 30 different species of poisonous plants.
1. Most likely to eat a rat
Giant Pitcher Plant: Nepenthes attenboroughii
Discovered more than 5000 feet above sea level on Mount Victoria in the Philippines, the giant, carnivorous pitcher plant secretes a nectar-like substance to lure unsuspecting prey into a pool of enzymes and acid. A series of sticky, downward ribs makes it nearly impossible for trapped prey to escape. The plant's 30-centimeter diameter is large enough to trap unlucky rodents, but insects are its most common meal. Pitcher plants, of which there are about 600 different species, tend to grow in nitrogen-deficient environments, and therefore get their nutrients from decaying victims.
2. Most likely to be in your garden now
Castor Bean Plant: Ricinus communis
Castor-bean plants can be purchased at just about any garden center, despite containing the deadly poison ricin. Amy Stewart, author of Wicked Plants and poisonous plant expert, has an affinity for the plant and grows several in her poison garden. Concerned gardeners can simply pluck the seeds off the plant, Stewart says, which is where the ricin is stored. Though the process to extract enough ricin and process it into a weapon is complex, Las Vegas authorities have discovered the toxin in a hotel room in February 2008, and the KGB used it to permanently silence opposition.
3. Most violently toxic plant in North America
Western Water Hemlock: Cicuta douglasii
Deemed the most "violently toxic plant that grows in North America" by the USDA, the water hemlock contains the toxin cicutoxin, which wreaks havoc on the central nervous system, causing grand mal seizures--which include loss of consciousness and violent muscle contractions--and eventually death, if ingested. Water hemlock is different from poison hemlock, Socrates' notorious killer, in that it contains coniine alkaloids that kill by paralyzing the respiratory system. Both are members of the carrot family.
4. The plant that killed a president's mother
White snakeroot: Eupatorium rugosum
Drinking milk from a cow that decided to chow down on white snakeroot could lead to deadly milk sickness, as was the case with Abraham Lincoln's mother Nancy Hanks. Every part of this perennial plant contains tremetol, an unsaturated alcohol that can cause muscle tremors in livestock before killing them. "People were trying desperately throughout the 19th century to figure out what was poisoning their animals," Stewart says. It wasn't understood until the turn of the century, when the U.S. Department of Agriculture pinpointed the cause and quickly got the word out. Now, white snakeroot still grows wild, but more control in the agricultural industry has helped to prevent cows from eating it.
5.The best plant to murder a dinner guest with
Monkshood: Aconitum napellus
Stewart was once asked what the best plant would be to murder a dinner guest with--after much deliberation she landed on monkshood. "You could just chop up the roots and make a stew," she says. "You don't need a chemistry plant to do it." The vibrant purple plant, commonly found in backyard gardens, is loaded with the poisonous alkaloid aconite, which tends to cause asphyxiation. While Stewart is certainly joking about cooking up a batch of monkshood stew, she urges anyone who has the plant in their garden to wear gloves when handling it.
6. Most gruesome killer
Common Bladderwort: Utricularia macrorhiza
This aquatic meat eater relies on several submerged bladders to capture prey such as tadpoles and small crustaceans. An unsuspecting passerby will brush against an external bristle-trigger, causing the bladders to spring open and capture it. Once inside, the victim dies of suffocation or starvation and then decays into a liquid that is sucked up by cells on the walls of the bladder.
7. Most animal-like
Venus flytrap: Dionaea muscipula
With the ability to clamp shut in a half-second, the Venus flytrap's reaction time seems fit for the animal kingdom. Insects need to touch two of the flytrap's hairs consecutively in order for the plant to react, but the precise mechanism that shuts the trap remains unclear. The Botanical Society of America notes that early theories suggested that a sudden change in the water pressure of cells triggered the response, but this theory has since been abandoned. It now seems that when the plant is touched, the electrical potential of the leaf is altered, triggering a host of cellular-level events.
8. The most enticing poison
Oleander: Nerium oleander
This extremely common evergreen shrub is one of the most poisonous plants in the world. "If I were a parent and covering every electrical outlet in the home to protect the kids, I would really have to ask myself why I had an oleander plant growing," Stewart says. The leaves, flowers and fruit contain cardiac glycosides, which have therapeutic applications but are likely to send someone into cardiac arrest should he eat part of the plant. Stewart points out that there is a woman in California currently on death row for trying to poison her husband with the plant, and two young boys were found dead after ingesting oleander a few years back. "People tend to be blasé, because the flowers are bright and pretty, sort of candy-colored. But it is a very poisonous plant that will stop your heart."
9. Best home-security system
Mala Mujer: Cnidoscolus angustidens
Mala mujer, which translates to "bad woman," can be found in parts of the southwest and Mexico and is covered with nasty thorns, which could be turned into makeshift barbwire if needed. The real danger, however, comes from the caustic, milky sap that can leak from the plant. The sap, a common feature among many plants in the Euphorbia genus, can cause painful skin irritations and unsightly discoloration. "I've had several people tell me they had euphorbia saps in their eyes," Stewart says. "And they had pretty surprisingly long-term eye damage."
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