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Archive for Friday, March 10, 2006

Gardening’s Least Wanted

March 10, 2006

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No doubt it all started innocently enough. Most disasters do. But by the time we arrived on the scene, things were wildly out of control.

Four years ago, my partner and I found our own version of what the writer James Thurber once called "the great good place." For Thurber, that meant a Colonial-era house in Connecticut. For us, a 1904 brick two flat on the north side of Chicago.

The house, while not dilapidated, had an air of genteel decline about it. It was obvious that no one who had lived there for the last half century had had much money to pour into improvements or even routine maintenance.

Walls were starting to crumble, the roof leaked, the century-old plaster rippled alarmingly throughout. The shocker, however was the backyard, where a previous owner had attempted to install an English country garden.

English gardens, of course, are famously irregular and naturalistic. The yard, however, had gone beyond "naturalistic" into something resembling a Rousseau junglescape. More than one friend invoked "Great Expectations" and Miss Havisham when viewing the scene.

The Frankenstein monster at the heart of it was a trumpet vine, a plant native to the Midwest, that had gradually engulfed the back fence and most of the garage.

How bad was it? Well, there were animals living in it, for one thing. And not just the normal birds and squirrels. Walking beneath an overgrown arbor one morning, I looked up and saw a possum clinging to a branch high overhead.

That was my introduction to invasive plants, a topic of more than passing interest in horticultural circles today.

"Invasive plants are the second biggest threat, behind development, to biodiversity in our eco system," says Janet Clark, director of the Center for Invasive Plant Management at Montana State University in Bozeman. "They create monocultures where the native plants suffer along with the things that depend on them: insects, birds, mammals. They throw off the whole ecosystem."

"It's a huge problem and it's getting bigger because of the increasing number of plants being introduced into non-native environments," says Kate Howe, coordinator of the Midwest Invasive Plant Network in Indianapolis.

Probably the most famous invasive plant is kudzu, an innocuous vine widely planted in southern rural areas half a century ago as part of a Federal anti-erosion program. Over the next 30 years, it exploded out of control, transforming thousands of acres into science fiction landscapes where every single object - buildings, trees, telephone poles - were encased from top to bottom in greenery.

Kudzu remains a problem to this day, even though other plants have superseded it in the eyes of researchers.

"Kudzu is the poster child for invasives," says Doug Bowen, president of the Southeast Exotic Pest Plant Council in Nashville, Tenn. "But there are other plants that are much worse."

Indeed, just about every state or region seems to be under siege by renegade flora of one species or another: purple loosestrife in the Midwest, Russian olives in Florida, tamarisk in the West, Norway maple trees in New England.

And crucially, for home gardeners, many got their start as a carefully tended seedling in somebody's backyard.

"About 60 percent of the invasive woody plants we see have escaped from home gardens," says Tom Stohlgren, director of the Institute of Invasive Species Science in Fort Collins, Colo.

Most, he adds, are exotics, or plants that have been deliberately brought in from other regions. "We move things around the globe today at an incredible rate. Every Web site is a potential port of entry."

Exotics often have an advantage over native plants, say experts, because they have evolved outside of the local eco system.

"With plants that have evolved over many years in a particular region," says Bowen, "there are usually environmental pressures, such as insects and soil and weather conditions, that keep them from becoming invasive."

A new plant, however, "has free reign. It starts reproducing exponentially in a greater capacity than it does in its home environment."

Both neglect, which was the case for us, and sudden or over development can lead to an infestation of invasive plants.

"Anytime you have disturbance or development," says Howe, "it's going to create conditions that are good for invasives."

Getting a handle on an invasive plant takes time and research. "The critical thing," says Clark, "is to be able to identify what you have and how it grows. Is it an annual? Is it a perennial that has a deep root system?"

If it's the former, meaning that it depends on seeds to reproduce from season to season, it's crucial to remove the plant before it flowers. If it's the latter, cutting the plant down is only the start of what in all likelihood will be a multi-year effort.

Herbicides can be helpful, but nothing really replaces the simple act of digging or pulling a plant up and discarding it.

In major infestations involving many acres, experts often recommend biological agents such as genetically altered beetles that are more or less programmed to consume a given plant.

"Some plants are really tough," says Clark. "In those cases, you never completely eradicate it but you knock it back to a level you can live with."

Which is pretty much where we are with our trumpet vine. We hacked it down, sawed the 5-inch trunk down to ground level and thought that was that.

Far from it. That summer, and for the next two summers, it continued to sprout madly all over the yard, next to the garage and even the next-door neighbor's yard.

We tried pulling it and dousing it with Round Up to very little effect. You may have bought the house, it seemed to be saying, but don't even think about the yard.

Finally, last summer, we decided to create a meditation garden, a process that involved digging out half the yard, laying down a black plastic tarp and filling the space with two inches of pea gravel.

There's still a few sprouts along the fence, but overall, we seem - for the first time - to have the upper hand.

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