A plant that makes poison ivy seem like a trip to the beach -- the Giant Hogweed -- was discovered in rural Michigan this week and removed by the local health department. The plant, which resembles Queen Anne's lace, can cause blisters, scars and permanent blindness if sap gets in your eyes.
But the the Giant Hogweed isn't the only baddy in the forest. Beware this list of plants found in the United States that unleash chemical warfare on unwary humans.
Poison ivy has a convenient rhyme to help people remember to “leave it be,” if it has “leaves of three.” Poison oak (above), a cousin of poison ivy (Toxicodendron radicans and diversilobum), also has leaves grouped in threes, but the wavy shape of poison oak's leaves resemble those of an oak tree, making for a nasty surprise for unwary gardeners. However, unlike an oak tree, the rash-inducing weed (Toxicodendron pubescens), has fuzz on its stems and the undersides of its leaves. Also, in spring it sports pale yellow flowers, then greenish-white berries.
Poison sumac (Toxicodendron vernix) also masquerades as a benign tree, the common and harmless sumac. Luckily gardeners don't have to worry about poison sumac as much, since it grows primarily in swampy soils. Poison sumac, oak and ivy all use the same chemical weapon, urushiol, to defend their turf from humans.
Burning a brush pile that contains one of the toxic trio can be release a smoky cloud of pain. Inhalation of the smoke can cause blood to fill the lungs. Pulmonary edema, as this condition is called, can be fatal, according to the National Library of Medicine's Toxnet.
The favorite food of Eeyore from the "Winnie the Pooh" stories and a patriotic symbol of Scotland, various species of thistles (pictured) don't need poison to put the hurt on humans. The sharp spines on the plants make it nearly impossible to pull from a garden bed without thick gloves.
The seeds of the beautiful morning glory (Ipomoea violacea or tricolor) contain a hallucinogen, lysergic acid amide (LSA). The indigenous people of Mexico used the seeds in ceremonies for centuries before the Spanish invasion. LSA is a natural relative of the synthetic psychedelic drug lysergic acid diethylamide (LSD).
Wanna-be Merry Pranksters eat morning glory seeds, hoping to get a LSD-like trip, but usually just fall asleep or freak out. Back in the '60s, one young man killed himself while under the influence of morning glory seeds, according to a case study in the American Journal of Psychiatry.
The plant tribe Daturae also contains plants people consume to get high, including the ostentatious ornamental Angel's Trumpet (shown here) and the agricultural nuisance Jimson weed. Both contain chemicals known as tropane alkaloids that cause delusions, delirium ... and death, as the Sun Sentinel reported.
In Germany, a teenager cut off his penis and tongue after ingesting Angel's Trumpet seeds, according to Sky News. However, the dangerous plants also produce medicines used to treat asthma and Parkinson's disease.
Socrates (469 - 399 BC) awaits his execution.
Poison hemlock works well to kill off any pesky philosophers, like Socrates (shown here), who might be corrupting the youth of the city-state. A native of Eurasia, poison hemlock's delicate flowers resemble Queen Anne's lace, but beware if the plant's stems have purple spots. Death or violent illness awaits foraging humans that mistake poison hemlock for a wild carrot or parsley, which hemlock's leaves resemble.
In Maine, one young man died after three bites of hemlock root in 1992, according to the Centers for Disease Control. In 2010, woman died after mistakenly tossing hemlock into her salad in Tacoma, Washington, reported KING5.com.
Pokeweed (Phytolacca americana) can be prepared as a traditional Southern soul food dish and grows as a weed in many yards. If cooked improperly, the plant can cause convulsions, vomiting, respiratory paralysis and even death, according to Iowa State University (PDF).
Brushing against stinging nettle results in intense itching and burning. Tiny stinging hairs coat the leaves of the plant (Urtica dioica), an invasive species in America that actually increases after mowing. Like pokeweed, this obnoxious weed can become a meal. Boiling in water kills the stinging chemicals and results in a dish that tastes like like turnip greens. Wild birds dine on the pokeweed's berries (shown here) unharmed.
The vibrant, red-and-green leaves of the castor bean plant (above) look stunning in landscaping designs. But the beauty hides a beast that has been used in poisoned envelopes sent to threaten the U.S. government. The seeds of the plant can be processed to yield the deadly poison ricin, as done by Walter White, the protagonist of the television show "Breaking Bad."
Oleander (Nerium oleander) grows in gardens around the world, but like the castor bean plant, its beauty hides mortal danger. Chewing a single leaf of the plant is enough to make a person gravely ill. Even honey made by bees from the oleander flower can poison a person, according to Medline Plus.