Wicked Plants (12 page)

Phototoxic plants harness the power of the sun to do their damage, using sap that burns the skin when exposed to light. In some cases, eating the plant or its fruits makes a person more susceptible to sunburn.

This weedy, invasive member of the carrot family looks like the older brother of Queen Anne’s lace. It’s a beefy, sturdy plant that grows over ten feet tall and pushes other plants out of their habitats in streams and meadows. It is also one of the most phototoxic plants you might encounter. One botany textbook shows a round slice of stem placed on a man’s arm; within a day, a circular red welt appears, and after three days, it begins to blister. The wound looks disturbingly like the severe burn a car’s cigarette lighter would cause.

Another member of the carrot family, this plant is susceptible to a disease called pink rot fungus (
Sclerotinia sclerotiorum
). The main defense mechanism is to produce more phototoxic compounds to kill off the fungus. Farmworkers and handlers of celery routinely get burns on their skin that show up under sunlight, and people who eat large quantities of celery are at risk as well. One medical journal cited the case of a woman who ate celery root and then went to a tanning booth, ending up with a severe sunburn.

This aptly named plant is also a member of the carrot family; its leaves resemble those of celery. The plants flourish in South Africa; tourists climbing Table Mountain near Cape Town are warned to avoid it. Simply brushing past it can cause a reaction, and hikers who accidentally break off a branch may suffer a severe rash from contact with the sap. The rash doesn’t appear for two or three days after contact with the plant and is made much worse by exposure to sunlight. The blisters can last a week or more and may leave brown spots on the skin for years.

Limes and some other citrus fruits contain phototoxic compounds in the oil glands found in the outer rind of the fruit. One medical journal reported on a group of children at a day camp who broke out in unexpected rashes on their hands and arms. Doctors determined that the only children who were affected were those who had gone to a crafts class. They had been using limes to make pomander balls, and piercing the lime peel with scissors spread enough oil on their hands and arms to cause a reaction.

Orange marmalade and other foods containing citrus peel or citrus oil may cause a reaction. Oil of bergamot, a small, pear-shaped citrus, is a popular fragrance ingredient; any citrus-based perfume or lotion could also burn.

The mokihana blossom is the official flower of the Hawaiian island of Kauai. Tourists are often presented with a lei made of the dark green citruslike mokihana fruit, which are about the size of grapes. The oils are also highly phototoxic: a few years ago, a tourist wore a mokihana lei for about twenty minutes. Within a few hours, a painful, blistering rash appeared on her neck and chest in the precise shape of the lei. It eventually faded on its own, but the marks remained visible for two months.

A number of plants used in herbal teas, potpourris, lotions, or other concoctions can be phototoxic, although symptoms may not show up for a few days. Medical case studies report reactions from Saint-John’s-wort, rosemary, marigold, rue, chrysanthemum, fig leaf, and others.

HIPPOMANE MANCINELLA

Tourists vacationing in the Caribbean or on the Central American coast are routinely warned about the hazards of the manchineel tree. As a member of the Euphorbiaceae family, it produces a highly irritating sap that can squirt out of the tree when a twig is snapped off. It also produces a toxic fruit that causes blistering in the mouth and makes the throat swell closed. Even lounging under the trees might be dangerous: rain dripping off them could cause rashes and itching.

The trees are irresistible to tourists. Despite her medical training, a radiologist visiting the island of Tobago was tempted to taste the green fruit that she found lying on the beach. When she took a bite, she found it to be sweet and juicy, like a plum. It took only a few minutes for a burning sensation to start in her mouth. Pretty soon, her throat closed so tightly that she could hardly swallow. The nearest medical remedy, a piña colada, helped a little, but probably only because of the milk it contained.

Captain James Cook encountered the trees on his voyage, and he and his crew also had a nasty encounter with the toxic tree. The
men were in need of supplies; Cook ordered them to begin by collecting some fresh water and chopping manchineel wood. Some of the crew members made the mistake of rubbing their eyes, and they were reportedly blinded for two weeks as a result. There’s no record of whether they actually burned the wood, but if they had, the smoke would have been particularly noxious.

The manchineel tree’s powers have been exaggerated in art and legend. The tree made its way into the 1865 opera
L’Africaine
by German composer Giacomo Meyerbeer. A heartbroken island queen who is secretly in love with an explorer throws herself under the manchineel tree and draws her last breath, singing:

Your gentle perfume, they say, gives a fatal bliss
Which for a moment transports one to heaven
And then brings on the slumber without end.

Meet the Relatives
Part of the Euphorbiaceae or spurge family, which includes a number of other trees and shrubs that produce milky, toxic sap.

Many plants that raise a rash on the skin or produce tiny, irritating thorns can also cause vision problems, including blindness. Here are a few of the most egregious examples:

Most people in the eastern United States know to avoid poison sumac, a close relative of poison ivy and poison oak. But one young man had to learn his lesson the hard way. In 1836, at the age of fourteen, Frederick Law Olmsted wandered into a patch of poison sumac and got covered in the sap. Soon his face was horribly swollen and he couldn’t open his eyes at all.

It took him weeks to make a partial recovery, but the damage to his eyesight persisted. He couldn’t return to school for over a year, and he once wrote that the problems with his eyes lasted much later into his life. It may be that this time off was just what the boy needed to nurture his interest in the outdoors and that it led to his career as a visionary landscape designer. He wrote, “While my mates were fitting for college I was allowed to indulge my strong natural propensity for roaming afield and day-dreaming under a tree.” Perhaps that year of daydreaming
provided the initial inspiration for New York’s Central Park, which he designed twenty years later.

This inconspicuous annual grows to two or three feet tall and produces small yellow blooms in the spring. It flourishes in dry fields and deserts throughout the United States. Its bitter taste discourages people from eating it, but cattle will graze on it, and the consequences can be deadly. Their tongues become paralyzed. They begin “head pressing,” butting their heads up against some hard object like a fence. Finally, the tansy mustard makes them go blind. Given the head pressing, the tongue paralysis, and the blindness, it is impossible for them to eat or drink, and they die of starvation and dehydration.

This Australian mangrove tree—another member of the highly irritating Euphorbiaceae family—has earned the common name “blind-your-eye” for the temporary blindness, burning, and itching that its milky sap can cause. If the plants are burned, the smoke will also seriously irritate the eyes.

In 1985 a New Jersey couple called an ambulance after developing a severe rash. They blamed it on some mysterious fuzzy bean pods they found in their bed. The paramedics developed the same symptoms, and everyone had to be treated at the emergency room. A nurse at the hospital even started itching after touching one of the patients. The apartment had to be completely decontaminated, including cleaning of all carpets and fabrics. The pods were identified as cowhage.

Cowhage is a climbing tropical vine in the bean and pea family. It produces four-inch-long, light brown, fuzzy pods that are covered with as many as five thousand stinging hairs. Even specimens that have been preserved in museums for decades can cause severe itching. If any of the tiny barbs get in the eyes, they can cause short-term blindness.

This small Australian tree, also called a native loquat, has long been rumored to cause permanent blindness to people who eat the small red fruits. There were several newspaper accounts of children going blind in the early 1900s, and in 1945 a newspaper reported that twenty-seven soldiers from New Guinea went blind after sampling the fruit. One possible cause is a fungus called
Gloesporium periculosum
that infects the tree. Australians know better than to take their chances.

A relative of datura, this South American plant can bring on an alarming case of “gardener’s mydriasis,” or excessive pupil dilation. Sometimes the pupil enlarges until it almost fills the iris, making it difficult to see. The effect is so frightening that it can send people to the emergency room in fear of a brain aneurysm.