Environment / Unusual Organisms

If plants were people, purple loosestrife would be Xena, warrior princess. Halfway between an herb and a shrub, it can reach several feet higher than a basketball player and it's plenty tough. One wildlife manager suggests the only effective way to get rid of loosestrife is to take a blowtorch to its roots. Yet a large stand of loosestrife in summer, with thousands of vivid purple plumes piercing the horizon, is a sight worthy of strong poetry. As naturalist John Burroughs wrote: "Your eye . . . will revel with delight in the masses of fresh bright color afforded by the purple loosestrife which . . . shows here and there like purple bonfires."

Charles Darwin, perhaps the founding member of the purple loosestrife fan club, wrote botanist Asa Gray, “I am almost stark, staring mad over Lythrum. . . .For the love of heaven, have a look at some of your species and if you can get me some seed, do!”

Yet this captivating plant is increasingly seen by North American botanists as an alien invader more insidious than the lowliest weed. Like many other plants and animals, usually foreign in origin, that mature fast, multiply prolifically, spread like wildfire, and often crowd out native species, loosestrife has been swept into the category of invasives. And in the past decade, control of invasive species has become the hottest of hot-button environmental issues. Six years ago the World Conservation Congress declared invasives second only to habitat loss as a threat to global biodiversity. Two years ago 500 scientists signed a letter imploring Vice President Al Gore to act against them. “We are losing the war against invasive exotic species,” the letter read in part. “We simply cannot allow this unacceptable degradation of our nation’s public and agriculture lands to continue.” Several months ago the Invasive Species Council was formed, cochaired by the secretaries of interior, agriculture, and commerce.

As pressure to do something has grown, the language used to describe invasives has begun to sound like wartime propaganda. Loosestrife has gone from being a nuisance and an interloper to a botanical bully and a green cancer. The plant no longer spreads; it invades, or infests. An appearance is an outbreak, a purple plague. Sometimes the fervor seems xenophobic: “The American people expect native species on their forest lands,” declared a forest service official recently.

All of which has made life a lot more complicated for Erik Kiviat, an associate professor of environmental studies at Bard College in Annandale-on-Hudson, New York, who has been studying loosestrife for nearly a quarter of a century. He’s an ardent naturalist, and an environmentalist to the bone—the sort of person who’ll study the fiber content of a candy wrapper before selecting the appropriate recycling bin. Yet because of his unpopular position that Lythrum may not be so terrible, his bemused colleagues call him, only half in fun, “the friend of purple loosestrife.”

In public, Kiviat adopts a precise, neutral tone when talking about the plant. He notes that the term invasive plant is an intellectual construct, reflecting cultural prejudices as well as scientific facts. In his writing, he’s less restrained, sprinkling his work with literary allusions to loosestrife from Hamlet and Wind in the Willows to remind readers that in other places and times it wasn’t a public enemy.

Sitting in his tiny office in a ramshackle field station at Bard, on the banks of the Hudson River, Kiviat says, “Twenty years ago the public thought raptors were bad and songbirds were good. Now everybody knows neither one is bad or good. They just are. Same with loosestrife—it just is. Maybe we should be asking: Why is this plant spreading now? What are we trying to accomplish by controlling it? If we succeed in getting rid of loosestrife, what do we get in its place? I think it’s fine to have our finger on the trigger when it comes to these plants. But why don’t we find out exactly what we’re shooting before we fire? Make sure it’s not a cow. Or a person.”

One of the attractions of Lythrum salicaria for Darwin was its exotic sex life. “In their manner of fertilisation these plants offer a more remarkable case than can be found in any other plant or animal,” he wrote. Loosestrife reproduction relies on a rare phenomenon Darwin called heterostyled trimorphism, the existence of three different flower types, each containing a sexual apparatus “as distinct from one another as if they belonged to different species.” He was interested enough to have grown specimens of loosestrife in his garden, and to have spent much of the summers of 1862 and 1863 snipping stamens, “castrating” the plants to use his unsettling terminology, and meticulously hand-fertilizing them with camel-hair brushes.

About a hundred years later, another passionate member of the loosestrife fan club began acquiring his affection for the plant at an early age. In the late 1940s Erik Kiviat’s parents—his father a carpenter and sometime labor organizer, his mother a photojournalist—founded a summer retreat catering to children of well-to-do New Yorkers. Jug Hill Camp was located in Dutchess County, a rural enclave halfway between New York City and Albany.

The county is dimpled with small ponds and wetlands, courtesy of glaciers that retreated 12,000 years ago. Much of the land was cleared for agriculture—mostly orchards and dairy and wheat farms—in the early 1800s. Because the region became a refuge for Gothamites who fancied themselves gentlemen farmers, it was spared the worst pains of development, and many parts of the county still look much as they did 200 years ago.

Kiviat’s parents needed a place for campers to swim, so they enlarged an existing pond behind the barn. Within a few years the loosestrife, which had been only one element of the diverse flora, surrounded the new swimming hole with a purple palisade. “When I was 4 and 5, I’d go down there and hang out by myself for hours, watching the sky and the bees and the butterflies,” says Kiviat. “I just thought the flowers were beautiful.”

Although he couldn’t have known it at the time, loosestrife encircled the pond so rapidly because it thrives on disturbance. A mature plant can produce as many as 2.7 million seeds–-each a bit like a grain of white pepper—in one growing season. And the seeds are durable: They can lie buried for years, then spring into growth when they’re brought to the surface—a phenomenon called recruitment from the seed bank. Minnesota researchers studying a wetland seed bank were recently disheartened to find that loosestrife seeds outnumbered other seeds ten to one.

Another reason the loosestrife flourished in the Kiviats’ pond can be found in its relative newness to North America. In the game of leapfrog that is evolution by natural selection, predators and hosts evolve together in a process called coevolution. In a new environment, with no predators, an exotic plant can theoretically run riot. Loosestrife seems to have hit the evolutionary jackpot. In its native Eurasia, where it has been a fairly unobtrusive member of the wetland flora since the last glaciation, more than a hundred different insects eat it. Here, it has few, if any, insect predators.This freedom from herbivores may explain one striking aspect of the plant’s behavior in North America: It grows triple the size it reaches on home ground. When plants need to defend themselves chemically against insects, they use a lot of their available energy in the process. It may be that in a predator-free environment loosestrife is like a country no longer at war that can reduce defense spending and invest in infrastructure.

The Effects of Introducing Purple Loosestrife
Purple Loosestrife in the Great Lakes Region