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.
Thomspon pond is about a ten-minute drive from the modest Dutchess County house Kiviat shares with his wife, Elaine Colandrea, a massage therapist. The pond is famous for the floating mat of vegetation on its fringes, unusual enough to have prompted the Nature Conservancy to buy it and the surrounding land in 1958. It’s a perfect example of a glacial pond. And a perfect place for Kiviat to show a visitor how loosestrife behaves in an undisturbed setting.
Kiviat has been visiting the site since he was in his 20s, snapping photos, drawing pictures, taking notes. He’s spent whole days in this and other wetlands of Dutchess County, sitting motionless in a canoe or on the bank. Everything from muskrats to bog turtles attracts his attention, and he had accumulated notebooks of observations on loosestrife before most people had ever heard of it.
These days, Kiviat has environmental studies classes to teach and grad students to supervise, as well as his work as executive director of Hudsonia, a nonprofit research institute, so he can visit for only a few hours at a time. Still, like an old-fashioned country doctor checking on patients, he continues to make rounds. He knows these patients so intimately that even the most subtle changes stick out. “I’ve been coming here for 25 years,” he says, piloting his dilapidated Toyota over back roads leading to the pond, “and there’s not a lot more loosestrife now than there was then. Some, but not a lot. You hear about the plant being so aggressive, but the landscape here hasn’t changed much.” In fact, the places where loosestrife has expanded are the places where humans have encroached on Thompson Pond. One is along a road that cuts the pond in half—the plant seems to like the salty runoff from de-iced blacktop. The other spot is near a feedlot for cows.
To understand the role of loosestrife in the ecosystem, Kiviat believes he must see it when it’s dormant. “The marsh can be a nasty place in winter, and it can be hard for animals to make a living,” he says. “A big plant like loosestrife, which takes two years to die back, might provide important shelter for something.” This nasty March morning a bitter wind rattles the cattails, and six inches of wet snow obscure the faint trail around the pond. Not that Kiviat seems to mind. He lingers to admire the wintry landscape, to puzzle over some animal tracks, to listen to red-winged blackbirds, all as if it were a balmy May afternoon.
The real object of his three-mile walk around the pond is to counter the notion that loosestrife creates a dead zone where no native plant can survive and no native animal sets foot. There are many small ways in which the plant is being integrated into the ongoing wetland life. For instance, he notices Virginia creeper climbing on the dead loosestrife stalks, which remain standing for two years. He spots three or four bird’s nests, including a grackle’s nest suspended between a loosestrife stalk and a swamp rose. “I’d say that’s three-fourths on the swamp rose and one-fourth on the loosestrife,” he says, scrupulously refusing to overestimate its importance. A chickadee flits by and perches briefly on a loosestrife stalk.
A little farther on he comes across unequivocal evidence that something is putting the loosestrife to positive use. Kiviat slits open a stalk with his pocketknife and a bright yellow insect larva gleams inside the pithy core. “That’s a Mompha,” he says, referring to a moth genus. “I see these fairly often, but because I’ve never seen the adult form, I can’t get it identified. For all I know, it could be a previously undescribed species.”
Discovery of a new insect species on purple loosestrife is unlikely, Kiviat says, but not impossible, given how little attention people pay to loosestrife ecology. Take the butterfly: The standard guide to butterflies of New Jersey says that only cabbage butterflies, the lepidopteran equivalent of trash fish, use loosestrife. But Kiviat, sounding slightly aggrieved, says that New Jersey loosestrife is visited by “big, beautiful, important butterflies—monarchs and tiger swallowtails and silver-spotted skippers.” A few observers, writing in obscure journals, have reported seeing the moth Biston betularia on purple loosestrife in Manitoba. The species has gained immortality in high school biology texts for switching colors from peppered to dark gray in the grimiest days of the industrial revolution.
Later, thawing out over a tuna melt and coffee in a local diner, Kiviat says the size of a plant’s insect fauna isn’t a matter of its popularity, but of its future. The more native insects an invasive plant attracts, the more chance some insects might decide to eat it. And if that were to happen, it could slow, or even stop, the invasion.
There are, says Kiviat, good theoretical reasons to believe that a problematic invasive might settle down without human intervention, though he concedes that it probably wouldn’t happen on a schedule that would make humans happy. Loosestrife has been here for more than 200 years; if something wanted to eat it, there has been plenty of opportunity. Yet the literature on invasives does record a few happy accidents: cases in which an invasive exotic met a native insect that said “Hallelujah!” The multiflora rose, for instance, spread unimpeded from the East Coast to the Rockies in a matter of decades, then encountered a mite carrying a disease of native mountain roses. Some of those mites switched hosts and are now marching east, destroying multiflora as they go.
The invasive exotic Eurasian watermilfoil, a likely escapee from home aquariums, began clogging waterways up and down the East Coast in the 1940s. A few years ago an alert biologist noticed unexplained declines of the invader. She investigated and learned that a native aquatic beetle had discovered the invasive, found it more palatable than the closely related native milfoil that had previously formed its diet, and started munching. Now when the weed becomes a problem, biocontrol specialists just beef up the beetle population.
Of course, Kiviat’s pleas for a wait-and-see approach to loosestrife may become moot if plans for insect biocontrol succeed. Since 1985, researchers centered at Cornell have been studying the possibility of controlling loosestrife by importing some of its European predators. After screening 100 or so insects that eat the plant in Europe, the researchers settled on 4 candidates—2 leaf feeders, a flower feeder, and a root feeder—deemed unlikely to misbehave in a new environment. (One test: The insects starved to death when offered anything but loosestrife to eat.) To date, the group has released more than 3 million insects on more than 1,200 loosestrife sites in more than 30 states.
The results are just now being tabulated—it can take three to five years for an insect population to get big enough to do major damage—but preliminary reports indicate success. Yet not even the most enthusiastic biocontrol freaks, as Kiviat sometimes calls them, think insects are the whole answer to loosestrife management: Hand removal and other methods will always be necessary.
Even if biocontrol were to eliminate loosestrife, there are plenty of other invasives to which Kiviat could turn his attention. He never misses a chance to visit a certain clump of reeds called phragmites in a pond in Central Park; he stops there when he’s in New York City the way some people make a point of popping into Zabar’s. Though deplored as an invasive, the plant has been in North America for 3,000 years. “People love that phragmites,” he says. “It looks nice, and the fact is, the birds use it constantly. Last time I was there I counted eight species in half an hour.”
Kiviat insists he’s not an apologist for the aggressive habits of loosestrife or other invasive plants. “Look, if you see a single purple loosestrife in a conservation area, I think you should pull it out by the roots and go back every year until it’s gone. There are situations where these plants are the enemy—but not in every situation.” Besides, he says, “sometimes when you get to know your enemy, he turns out to be your friend.”
The Effects of Introducing Purple Loosestrife
Purple Loosestrife in the Great Lakes Region