The other invasive vines arrived as decorative plants in the 18th and 19th centuries and can still be purchased at many nurseries.
They landed in the New World without their native pests and diseases, which kept them in check back home. Birds and other creatures love the forbidden fruit and excrete the seeds hither and yon. The vines' fertility is awesome: They produce more seeds than native plants, and the seeds may survive in the ground more than a decade, waiting for the right moment to pounce.
Some vines don't need seeds to spread. A scrap of English ivy tossed in the dirt can grow up to be a tree-killer. Oriental bittersweet is especially cunning. It can wait years in the shade until one day a break in the forest -- caused by a storm, or a developer -- gives it enough light to scale tall trees in a single season.
Kudzu is king of the growth spurts, about 60 feet during the spring and summer growing season. Mile-a-minute grows 25 feet; porcelainberry, 15 feet.
In contrast, native vines such as grape, greenbrier, Virginia creeper, even poison ivy do not subjugate -- they participate in landscapes.
But the real enemy is us. Our yards are the main source of the vines loose in the wild. They were planted once upon a time as ornamentals by the people who previously owned our houses.
"The park was surrounded by Victorian mansions ever since inception," says Sue Salmons, resource management specialist for Rock Creek Park. "To gardeners, the more exotic the plant the better, especially Victorian gardeners."
Anyone can have a green thumb with invasives.
"These plants are more than low-maintenance, they're no-maintenance," says John Peter Thompson, chief executive officer of Behnke Nurseries. "Basically all you have to do is get them into place and walk away."
Thompson won't sell porcelainberry and Oriental bittersweet. He does sell English ivy -- with a warning label.
Now, after generations in the New World, vines are a leading example of the larger problem of invasive plants taking over the woods. And invasive plants fit into the overall grim picture of all invasive species running amok, from zebra mussels to snakehead fish.
Yet while a single snakehead becomes a monster celebrity, the quiet creep of millions of vines can pass barely noticed.
"Everybody and their dog had to be out at that lake getting their picture taken for one fish," Bergmann says, referring to the lake in Wheaton Regional Park where a snakehead was caught in April. Meanwhile, "this whole park, this whole county is being inundated by these invasive species plants that are changing the ecosystem even as we speak."
Cutting Remarks
Steve Young remembers the day he discovered the threat of vines.
He was walking in the Long Branch Nature Center park next to his Arlington neighborhood in the fall of 1994. He trod along one of his regular paths through the quiet forest when something caught him by surprise: A wooden bench beside the path was engulfed in ivy.
"I had this 'that's-not-right!' reaction," he says during a recent visit to the bench. "I just started pulling ivy off."
Volunteer vine-cutters often date their activism to such epiphanies. All at once they notice the shocking transformation of a favorite piece of land.
Young, now 50, an information technology specialist with the Environmental Protection Agency, began regular trips to the park to attack the ivy mat that covered the forest floor. Gradually other weed warriors began to join forces with one another and county park rangers. At their urging, two years ago Arlington became one of the first jurisdictions in the region to hire a full-time invasive plant fighter. The citizen volunteer group RIP now has about 30 members.
Parallel volunteer efforts have sprouted around the Beltway. One of the oldest is Weed Warriors, created by Bergmann in Montgomery County in 1999. It has more than 250 members.
On a recent afternoon, Young hikes through the Long Branch woods, pointing out progress.
The wisteria thicket that used to be near the outdoor amphitheater is gone. That vine was a threat to national security: It helped conceal the hiding place where Russian handlers left $50,000 for FBI spy Robert Hanssen in 2001.
The woods are opening up, providing breathing space for the return of native plants. Some of the young trees are still stooped -- not yet recovered from their burden of vines. Trunks have twining scars where vines once girdled them.
