I just finished reading a fun and somewhat terrifying book called Wicked Plants:The Weed That Killed Lincoln’s Mother and Other Botanical Atrocities, by Amy Stewart. She covers several hundred dangerous plants from around the world, including plants that are toxic to ingest or to touch, plants that are so invasive they’re destroying ecosystems, plants that explode, and much more. Here are a few tantalizing bits…
1. An alarming number of common houseplants are quite toxic, and not just to pets. Philodendron and Peace Lilies can cause stomach problems if ingested, but also allergic reactions from skin contact. Ficus and Rubber trees contain latex, and individuals with a severe latex allergy can experience anaphylactic shock just from casual contact. Just pruning your English Ivy can be problematic, as the sap can cause nasty blisters. And while people worry about poinsettias at Christmas, though they’re not particularly dangerous at all, a few bites of an Easter Lily can cause kidney failure and death in a day or two for pet cats.
2. A surprising number of common food items are toxic when not prepared properly. Elderberry jam and wine have been around for generations, but raw elderberries poisoned a group of people in 1983. Undercooked red kidney beans can cause severe gastrointestinal problems, and poisoning often occurs when they’re not fully cooked in a slow cooker. You’ll never find raw cashews in stores, because their shells contain the same oil found in poison ivy; cashews are always sold shelled and cooked to ensure the oils are gone. Even burning cashew wood produces smoke that can damage the lungs.
3. Some plants only cause problems when combined with sunlight, as I learned the hard way a few years ago with Common Rue. These plants contain phototoxins that must be exposed to UV light to be activated. Generally, what happens is that you prune or work around these plants and make skin contact, and within a few hours you have a blistery rash. Oils from citrus rinds can cause this problem, especially limes, and so can the Mokihana fruit, which is frequently made into leis and placed around the necks of Hawaiian tourists. Rosemary, marigolds, and St. John’s Wort have also been reported to cause phototoxic rash.
4. You almost certainly have a dangerous plant or two in your yard right now. Hydrangea blooms contain low levels of cyanide. Azalea is so toxic that honey made from its blooms can cause heart problems and dizziness. Morning Glory seeds can cause an LSD-like trip, which teenagers have been known to exploit (albeit dangerously – side effects include high heartbeats requiring hospitalization). Hyacinth and tulip bulbs produce sap that causes serious skin irritation and can be even more dangerous if the bulbs are consumed by dogs. Lantana berries are especially toxic when still green, and can cause heart and vision problems, among others. See what I mean?
5. If you’re wondering about Abraham Linkcoln’s mother… the cause of her death was “Milk Sickness”, caused by White Snakeroot (Eupatorium rugosum). This common weed grew in pastures and was eaten by cows. The deadly toxins killed the cows eventually, but not before they were passed along in the cow’s milk to unsuspecting humans. Cows and humans all died in the same way: weak, vomiting, and delirious. Milk Sickness continued to cause illness and death until the 1920s, when White Snakeroot was finally understood to be the cause and farmers worked to eradicate it from their fields.
There are dozens more formidable and fascinating plants in Stewart’s book – enough to make you feel a little wary of going out to work in your garden again. A little knowledge can be a dangerous thing sometimes!