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Plant invaders—non-native species that grow out of control—cost the American economy more than $120 billion a year. Most of them don't get here by accident or mischief, but by invitation: we bring them here to beautify our yards.

As Jane Stratton (’72 Fine Arts, Education) strolls along her rows of snapdragons and blanket flowers, she scuffs a fleshy, ground-hugging plant.

"I don’t know what that is, but it’s all over," she says.

Stratton runs Sunshine Crafts, a business that offers a u-pick garden, subscriptions for a weekly vase of fresh flowers, and arrangements of dried flowers. Her two-acre plot just outside of Pullman brims with gladiolus, daisies, peonies, and more.

Like all avid gardeners, Stratton has encountered her share of aggressive plants that don’t stay where she puts them. About 10 years ago she planted a silvery Artemisia she thought would be lovely in dried arrangements.

"As it got time to harvest it, I noticed it growing everywhere along the roadsides," she recalls. "And I thought, why did I plant this to  begin with? It is pretty, but it just self-seeded.  It’s been really hard to grub out."

Now Stratton is a lot more careful about what she buys, and she keeps a close eye on her living inventory. Any plant that starts spilling out of its assigned space gets a swift correction.

"That’s the key," she says. "A little elbow grease can go a long way in the beginning, rather than trying to stop this stuff once it’s already  established."

Richard Mack (’71 Ph.D. Botany), an ecologist at Washington State University, visited her garden soon after the Artemisia episode and became a big fan.

"She told me what she did, and I thought, gosh, this is exactly what needs to be done. This is extraodinary. I was really struck by her conscientiousness in taking something out of there that looked like it was going to jump the fence," he says.

Mack has devoted his career to understanding how plants that are native to a place "jump the fence." In his view, Stratton is on the front lines of an all-out war against botanical invaders.

While the military metaphor might seem alarmist, the scale of intrusions, and the damage they do, meet any reasonable criterion of "invasion." A 2000 study by researchers at Cornell University estimated that invasive species—plants, animals, and microbes—cost American businesses and taxpayers at least $122 billion every year in damaged property, lost productivity, and control efforts. More subtle, and perhaps more costly in the long run, is the damage done to natural communities. Invasive species crowd out natives, mangle food chains, increase fire frequency, and speed erosion. They are the main factor in the decline of nearly half of our threatened and endangered species.

The kicker to this tale is that most plant invaders didn’t get to the  United States by accident. Some were imported as potential forage or other crops, but the vast majority are ornamentals. We brought them here not to feed ourselves or our livestock, but to beautify our yards.

The same thing has happened all over the world. During the past decade, Mack has been asked to review biosanitation protocols written by the governments of India, China, and Taiwan, all of which are struggling against current invasions and are anticipating more, as expanding trade and improving infrastructure help alien species reach new territory.  Everywhere he goes, the pattern is the same: plants imported to beautify gardens or parks jump the fence, run rampant, and disrupt native plant and animal communities in profound and sometimes dramatic ways.

A few years ago, for example, Mack found himself atop an elephant in  India’s Corbett National Park. He’d been invited by conservation officials there to consult with them about lantana (Lantana), a sprawling shrub from South America that has escaped cultivation and now clogs hundreds of thousands of acres of open woodlands with impassable tangles of floppy branches. As their elephants waded through the snarl, Mack and his hosts spooked a leopard.

"The poor cat was trying to get out of our way and flee, and he was having all the difficulty in the world," recalls Mack. "He couldn’t spring. It was the most unnatural movement for a leopard that you can imagine. Normally he could have been out of there lickety-split. Instead, I was on this elephant, looking down, and here was this guy body-surfing over the  lantana, trying to get out."

What dollar value do we put on a leopard’s ability to spring?

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