In Praise of Poison Ivy

Deadly. Powerful. Beautiful. The much-hated plant called poison ivy is all of these—and more.cover--in praise of poison ivy--sanchez

Poison ivy has long irritated humans, but the astounding paradox is that poison ivy is a plant of immense ecological value. In Praise of Poison Ivy explores the vices and virtues of a plant with a dramatic history–and a rosy future. Once planted in gardens from Versailles to Monticello, poison ivy now has a crucial role in the American landscape.


Poison ivy grew in the manicured gardens of Versailles.

Poison ivy grew in the manicured gardens of Versailles.

Since the time of John Smith and Pocahontas, the American landscape has changed in countless ways—many obvious, some subtle. This book will reveal why there is far more poison ivy on the planet now than there was in 1607, with lots more on its way. It examines the ecological reasons for poison ivy’s rosy future, note the effects of climate change on native plants, and investigate the valuable role that poison ivy could play in our changing world.


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From the Book:

In Praise of Poison Ivy

The Secret Virtues, Astonishing History, and Dangerous Lore

of the World’s Most Hated Plant




It’s not actually possible to get poison ivy from opening this book.

It is, however, possible to get poison ivy—the exquisite torture of that insanely itchy rash—in a bewildering host of other ways. The inconspicuous little plant contains one of the most potent toxins on earth. A chemical called urushiol, found throughout the plant, can cause an allergic reaction in approximately 85% of humans, and dermatologists have estimated that one ounce of urushiol would be enough to give a rash to thirty million people. The stuff is plant plutonium.

Even if you haven’t had the pleasure of meeting poison ivy in person, you’ve heard tales of it, I’m sure. For centuries, poison ivy has bedeviled, inconvenienced, and downright tortured the human race. But why is poison ivy apparently on a mission to give us grief, from itchy ankles to life-threatening medical emergencies? What is the purpose of a plant expending precious energy to produce such a powerful toxin?

It isn’t hard to imagine that it’s all an evil plan—nature’s revenge, so to speak. Because poison ivy goes out of its way to target humans.

Yes, indeed. Just us. The astounding paradox is that poison ivy is a plant of immense ecological value. Wild mammals from mice to moose, livestock like goats and cattle, hundreds of species of insects—all defy poison ivy’s nasty nature and feast on its leaves. Bees and butterflies suck its sweet nectar. (Yes, it has flowers.) Woodpeckers, wild turkeys, robins, and bluebirds all feed with gusto on its fruit. Cardinals are even known to line their nests with fuzzy poison ivy rootlets, in which the young birds nestle comfortably.

Don’t all these creatures get itchy?051

Nope. Just us.

Over the years, after many bouts of blistered ankles and sore elbows, I’ve learned to look for poison ivy wherever I step. And, as often follows, with increased awareness comes…well, perhaps not love, but…let’s say, appreciation. I’ve developed a grudging admiration for poison ivy’s beauty, savoring its ruby leaves in spring, its gold and scarlet plumage in fall. I’ve found I have to watch my step almost anywhere I go: poison ivy is a plant with a broad tolerance for an enormous range of habitats, thriving coast to coast, from mountains to desert. I’ve seen the familiar three-parted leaves lurking in dark Canadian forests and sprawled in the sun on the beaches of Cape Cod. [Figure I-1 near here] I’ve avoided their toxic touch in Appalachian wilderness and in Manhattan’s Central Park. Poison ivy hangs out in a humid Louisiana bayou just as comfortably as it does in Arizona desert, where in fall the crimson leaves glow like Christmas tree lights against the canyon walls.

Okay, pretty leaves, yes. But. Still. That itchy problem just won’t go away. Once you’ve tangled with poison ivy, you never quite forget it. I think it’s fair to say that no other plant in the world has been detested with such bitterness. It comes as a surprise, therefore, to find that poison ivy was for centuries a popular—and very expensive—garden plant. I’m serious. There was a time, centuries ago, when seeds of poison ivy were almost literally worth their weight in gold. Planted in the gardens of emperors, presidents, and kings, poison ivy was displayed like a captive tiger equally prized for its beauty and its deadliness.

Alas for poison ivy, that’s no longer the case. Understandably so—no one wants a plant that causes a horrible rash twining around the picnic tables, the swimming pool or the playground swings. So poison ivy is drenched with herbicides in backyards and schoolyards, hiking trails and campgrounds across the nation. I would guess that few plants on earth undergo such a barrage of deadly chemicals. Yet poison ivy remains.

How does poison ivy do it? What’s the secret of its success? Hundreds of thousands of other species of plants are in danger of extinction: ferns, wildflowers, trees, vines. It might be worthwhile to examine how it happens that this tough little plant can defy humans’ best efforts to get rid of it—and it might be worth our while to give a thought to the possible effects of spraying herbicides around the swing sets, the swimming pool, and the picnic tables.

In writing this book, I’ve followed poison ivy’s trail as the despised plant weaves its way through history and over the landscape, and the meandering vine has led me into places I never thought to go. You can’t research poison ivy without delving deep into the history of the American wilderness, and the American backyard, and discovering how they’ve changed over the past three centuries. You can’t study poison ivy without learning about the complicated tangle of its interrelationships with the wildlife it nurtures, and with plants that it helps or harms.

Poison ivy, I’ve found, is a lens through which to take a broader look at the whole green world around us. The human love/hate relationship with this plant is a microcosm of our changing attitudes to nature over the centuries. Poison ivy’s ups and downs mirror our drastically changing landscape and climate. And poison ivy’s future is rosy: turns out the plant thrives in the exact conditions that climate change is now imposing on our stressed planet. A plant, perhaps, worth studying.

Most of all, I’ve discovered that the story of poison ivy is inextricably intertwined, for good and ill, with people. It’s part of our history, a plant both adored and reviled by our ancestors. We’re locked in a toxic battle with it here and now. And in spite of all our efforts to eradicate it, I’m absolutely certain that poison ivy will be there in the future, twining around the ankles of our descendants.poison ivy leaf close


Chapter 1                   The Poysoned Weede

Jamestown, Virginia, 1607


When Captain John Smith first set foot on the shore of the New World, he had little idea of what hazards awaited him. “Virginia is a country in North America,” Smith wrote of the great green land that stretched before him on that spring morning. “The bounds thereof on the east side are the great ocean….but as for the west thereof, the limits are unknown.” Smith and his band of nervous colonists hoped to reach the Pacific Ocean in a few days’ journey. They had only the haziest conception of what lay over the horizon—or just around the corner.

John Smith was certain, however, that enemies lurked in this new land. He had read accounts of previous settlers, and he expected to find Virginia thickly populated with “savages.” So Smith was wary and well-armed with musket, sword and metal breastplate. He was prepared to face any dangerous natives, and he knew they could be unpredictable, ubiquitous, and savage.

But Captain Smith had human adversaries in mind.


The three-leaved plant, creeping up tree trunks and spreading over the forest floor, appeared harmless at first. Smith, an unusually observant explorer for his time, noticed the inconspicuous leaves that brushed against his boots as he strode into the forest. He commented that it was “much in shape like our English Ivy,” the graceful vine that covered the walls of manors and churches back home. However, it wasn’t the same old ivy he was used to, as he soon discovered.

Poison ivy (Toxicodendron radicans) and its relatives, poison oak and poison sumac, were completely unknown to the Old World. Europe, of course, is well endowed with thorns, thistles, and stinging nettles—plants that let you know in no uncertain terms when you’ve encountered them. But the colonists were unprepared for a plant that could wreak so much havoc so stealthily.

Photo courtesy Denise Hackert-Stoner, Naturelogues

Photo courtesy Denise Hackert-Stoner, Naturelogues

Poison ivy’s chemical warfare against the human race is surprisingly subtle—when poison ivy attacks, you don’t realize what’s happening. The leaves caress your skin as you walk past, and only hours or days later do the results become clear. A chemical compound called urushiol, found throughout the plant, is a powerful allergen which triggers a delayed dermatitis reaction in most—but mysteriously, not all—humans.

And Smith, like many other overconfident explorers, fell into the plant’s trap. “Being touched,” he wrote, “the poysoned weed causeth rednesse, itchynge, and lastly blisters.” John Smith was certainly not the first human to get poison ivy, but he was the first to describe the plant and its resultant rash in writing, and his description of the symptoms is clinically exact—it’s not hard to imagine that he wrote from first-hand experience.

Short and stocky, with a big red beard that almost hid the metal breastplate on his chest,

John Smith was young man when he joined the Jamestown expedition—only twenty-seven. But he already had years of military experience under his belt, and had travelled thousands of miles as a mercenary, adventuring in exotic places like Transylvania, Russia, and Constantinople. The thought of exploring a wilderness, even one laced with poison ivy, didn’t faze him at all.

He and the other would-be colonists, a group of just over a hundred men and boys, were bankrolled by the wealthy merchants of the Virginia Company of London, who were hoping to make a financial killing on the venture. The colonists also were eager for quick riches—in fact, everyone involved in the venture had, as John Smith irritably put it, “great guilded hopes.” In the forests of Virginia, green as the Garden of Eden, many Englishmen assumed that gold would be theirs for the taking, handed over by friendly natives eager to gain the benefits of civilization. But the colonists should have remembered that in Eden, things were not always what they seemed…