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I Love You, I Love You Knotweed

The Knotweed Project excoriates -- yet cultivates -- an ornamental plant run amok

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"We're using them for an exhibit, but really, I think they're using us," says architect and Ground Zero volunteer Christine Brill as she attends to an innocent-seeming knotweed plant growing in a window of the six-foot-wide Skinny Building Downtown.

 

Several dozen knotweed plants in five-gallon buckets line up like a belligerent, ragtag militia against the two-story wall of windows facing Fifth Avenue and Wood Street.

 

"I can't believe we're actually taking care of knotweed. I even found myself weeding the knotweed ... it feels wrong," she adds uneasily, as she continues to give aid and comfort to the enemy, hiding out in this aboveground bunker of the beleaguered Fifth-and-Forbes corridor.

 

Based on the ecological rap sheet of the plant in Western Pennsylvania, knotweed ought to be drug out in the street and shot. If only it were that easy. "Japanese knotweed invades ..." reads the lettering on the Skinny Building windows. Indeed, over the past century, knotweed has aggressively overrun large swaths of land in Western Pennsylvania and shoved out native species. And, like a B-movie alien, it's virtually unkillable without massive amounts of pesticide (although scientists are researching its natural enemies).

 

Legend has it that the species, originally from Japan, was brought here as an ornamental in the 19th century by landscape architect Frederick Law Olmsted, famous for designing Manhattan's Central Park. Pretty enough in small doses, knotweed loosed itself from the strictures of its Victorian gardens and spread voraciously across North America and Europe.

 

An entirely new batch of this prolific plant can grow from a bit of root only half an inch long. A tiny shoot can produce a whole new stalk, and plants can grow inches in a single day. Its woody, bamboo-like fronds and broad leaves quickly form a dense stand on any exposed ground, hogging the light from anything else.

 

Knotweed tends to establish itself on disturbed soil, while areas with established cover resist it. Thus, Pittsburgh's post-industrial riverbanks are especially vulnerable to knotweed.

 

In fact, this one-time hothouse flower may be the "world's largest female," as British scientist Hamish Kidd puts it. Although knotweed has small white flowers, it more often propagates itself by sending up new shoots from an existing root. Thus, it's a lot like crabgrass ... nuclear crabgrass.

 

"If you look at one hillside that's covered with knotweed," says Knotweed Project participant and Three Rivers Second Nature team member Noel Hefele, "that might be all one plant." While some knotweed observers believe there may be two varieties that seem to interbreed with one another, research shows that Europe's -- and possibly North America's -- knotweed is a single clone, which makes it a more creepily dominant plant monopoly than even Archer Daniels Midland could've created.

 

A Three Rivers Second Nature ecological survey indicates that knotweed now occupies six percent of the riverbanks and streambanks near Pittsburgh, and eight percent of the waterfront in Allegheny County. Only a few other species have such a large share of real estate. It's safe to say that, thanks to knotweed, even if Allegheny County's rivers and streams are cleaned of pollution and industrial debris, it will be exceedingly hard to return the banks to their pre-industrial ecology.

 

"Some of the patches are so big," says Hefele, "it's unrealistic to think you can get rid of it in Western Pennsylvania."

 

The Knotweed Project contains within itself a weird mix of contradictions. The collaborators want the public to start paying attention to knotweed and its detrimental effect on our region's ecological balance. But, in drawing attention to the invader, they can appear to promote it.

 

Knotweed Project got the most public attention, appropriately enough, at the Sprout Fund's recent Hothouse event -- which usually has nothing to do with botany.

 

"People were asking, 'What's your message?'" recalls Brill. They wanted to get people to think about the astonishing omnipresence of the weed and its ecological effects, yet "people were attracted to it, because the leaves are soft and seductive and pretty." Some asked where they could buy plants for their gardens. Others were horrified to see knotweed in the spotlight, Brill recalls: "They said, 'This is evil!'

 

"We don't say it's evil," Brill concludes.

 

Adds Hefele philosophically: "There's six billion people on the planet. Who's the more invasive species?"

 

Instead, the Knotweed Project team says that they simply want the public to learn about it, even come to terms with it. Its spread, after all, is but one consequence of the many bad environmental choices made by our industrial-age ancestors.

 

In fact, this spring, Venture Outdoors (formerly the Western Pennsylvania Field Institute) responded to the knotweed menace with their program "If You Can't Beat It, Eat It," featuring knotweed "cuisine." Tender knotweed shoots, it turns out, taste like rhubarb -- although some were weirded out by its "mucilaginous" texture, says Hefele. And just as knotweed itself has colonized the world, knotweed recipes -- knotweed wine, knotweed cookies -- have finally begun to spread over the World Wide Web. Perhaps pancakes are next: Hefele says knotweed's a member of the buckwheat family.

 

Looking for more uses, Hefele, who looks a bit like a wood sprite himself, has figured out how to fashion panpipes and flutes from knotweed's bamboo-like stalks.

 

In its native Japan -- where, Hefele says, it tends to stop growing at two or three feet, not Pennsylvania's gargantuan 10 feet -- knotweed fills a vital, specific niche in the island's ecosystem: colonizing burned, igneous ground left after a volcano eruption.

 

In fact, as with another urban pioneer, the cockroach, it's easy to imagine knotweed being one of the sole survivors of a nuclear blast. And the way this world's going, if you don't like eating bugs, you better start practicing those knotweed recipes.

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