To free urban forests from invaders, some weigh ban on noxious plants

English ivy and other invasive plants are strangling Seattle's forests, spurring a multimillion-dollar plan to restore the woods. It is also suddenly putting homeowners and garden stores here under scrutiny.

Experts, environmentalists and even some public officials are raising questions: Where's all this stuff coming from? Should it be outlawed?


		Dan DeLong / P-I
	Unchecked ivy covers trees in Kinnear Park in Seattle and can kill them. The damage worsens in winter.

Evidence of the weedy invaders is easy to find across the city, especially at this time of year. Maples on Queen Anne's western slope have dropped their leaves, exposing twisting cables of ivy that swarm up trunks and reach high into the trees' canopies, snapping tender branches.

In the greenbelt hugging Admiral Way Southwest, north of the West Seattle Bridge, dozens of trees are shrouded in ivy -- a chokehold that will tighten through the winter.

Many nurseries and big-box home-improvement stores in Seattle and across the state sell English ivy by the flat. The plant is intended for landscaping, but the fast-growing ground cover can be difficult to control.

"It's potentially very serious," said Sasha Shaw, an education specialist for the King County Noxious Weed Control Board. "It's really evident in the cities right now. That's where the plants are escaping more often."

Some people concerned about the health of urban forests believe it is time to ban the sale of the most aggressive invasive plants. Others think it's too late.

In 2002, Oregon put some forms of ivy on its quarantine list, banning their sale. In Washington, there are no controls. Ivy isn't even included on the state's list of most serious offenders, ranking among the least threatening of noxious weeds.

When ivy is spotted attacking trees in natural areas, such as on the fringes of Schmitz Park in West Seattle and Interlaken Park on Capitol Hill, it likely got there one of two ways: The plant either crept from neighboring yards into the woods, or birds ate the plants' berries and spread the seeds.

Ivy isn't the only non-native, ornamental plant to turn up in the woods. Others include English holly and laurel, and Himalayan blackberry, planted historically as crops.

"If we know something is a bad actor, nobody should be growing them," said Sarah Reichard of the University of Washington's Center for Urban Horticulture.

But state officials and some in the nursery business argue that the plants can be safely and responsibly grown -- if people are educated about the risks.

Besides, they say, ivy is so prevalent in our woods today that a ban would accomplish little. Instead, efforts should focus on increased education and volunteer efforts to pull the tenacious weeds.

"What would stopping ivy coming into this state accomplish at this point?" asked Mary Toohey, an assistant director and invasive weeds expert with the state Department of Agriculture. "It's loose. We need to deal with it in different ways."

Touted for climbing trees

ALSO IN THIS REPORT

How our urban forest could turn into an 'ivy desert'
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How invasive ivy kills
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Rating the health of Seattle's forested public parks

See more stories in this special report

A tag in a pot of English ivy for sale at The Home Depot crows about its "beautiful evergreen foliage" and proclaims it "ideal as a ground cover ... or as a vine for climbing tree trunks and walls."

Other garden stores sell varieties of the vines that aren't specifically English ivy, but cousins that are likely equally invasive.

Research from the UW scheduled for publication early next year in the journal Biological Invasions shows that more than 80 percent of the ivy found in a survey of 119 samples clipped from 58 public parks from southern British Columbia to northern Oregon is actually the Irish or Atlantic form.

"There are things going on in our forest that we don't know about," said Reichard, one of the paper's authors.

The scientists used DNA analysis to identify the plants, she said, because they can look very similar and sometimes mate with each other. There are hundreds of English ivy varietals alone.

That complicates the prospect of a ban.

Oregon currently quarantines some kinds of English ivy, but not all of those identified as problematic are prohibited.

"We need to look at tightening that up at some point in the future," said Tim Butler, manager of the noxious weed control program for the Oregon Department of Agriculture.

"It can be a real balancing act. You've got plants that can be people's livelihoods that you're looking at listing as noxious weeds."

The Washington State Nursery and Landscape Association prefers educating plant sellers and the public and the voluntary restriction of sales. That applies to ivy, too.

The plant can be a problem if it escapes into the woods, said Jeanne McNeil, executive director of the association. "However, if it's contained in a planter on someone's patio ... then it can be an evergreen vine that they can enjoy in the winter."

When it comes to banning plants, "it's not just harming the people who produce and sell them, it's also denying the homeowners of choices," she said.

Despite the tag promoting outdoor use, Home Depot spokeswoman Kathryn Gallagher said in an e-mail that the stores "market ivy for indoor application only, which is one of the more popular varieties of trailing indoor houseplants."

'They're gaining on us'

This past summer, work was completed on a pilot project in which five participating Puget Sound-area nurseries continued to sell plants known to damage urban forests, but promoted less-invasive alternatives.

Results from surveys filled out last spring and in 2004 showed that 86 percent of the customers appreciated getting information about alternative plants from nursery staffs.

Sales of the invasives -- three kinds of ivy, English holly, fennel, David's butterfly bush and Yellow Flag Iris -- plummeted 43 percent. Sales of plants suggested as a forest-friendly alternative increased by 23 percent.

The voluntary effort was a success, said the UW's Reichard. "People don't want to be buying and selling invasive species."

Olympic Nursery in Woodinville, which sells larger plants and no ivy, supports banning the sale of invasive varieties of the vine. But owner Tom Quigley agrees that education and voluntary reductions are preferable.

"Who's going to enforce it?" he asked. "Are you going to have the ivy police out?"

Mayor Greg Nickels hasn't ruled out regulating the sale of ivy.

"We're going to have to take a look at that," he said in a recent interview. "As we make these investments in the publicly owned forest, we don't want these things to come back and sweep through the forests."

Right now, a ban is premature, Nickels said. "I don't think we're at that point. If we're unsuccessful in educating people, that's a logical next step to consider."

It's up to the state Agriculture Department to determine which plants are banned statewide. Currently, 62 terrestrial species are on the quarantine list, including kudzu and Scot's broom.

"I think they're gaining on us," Toohey said of the invaders. "It's a serious problem, and it's getting more and more serious."

MORE INFORMATION

P-I SPECIAL REPORT

Read the newspaper's report examining threats to Seattle's forests online: www.seattlepi.com/specials/urbanforests.

HOW TO HELP TREES

Ivy can be pulled by hand or by using pruners or loppers. If it has grown up a tree, remove the bottom few feet of ivy and clear it from the tree's base. The higher vines will die.

ON THE WEB:

No Ivy League: www.noivyleague.com

Ivy Out: www.ivyout.org

King County Noxious Weed Control Board: dnr.metrokc.gov/wlr/lands/weeds/weed_control_board.htm

Marianne Binetti in the P-I: goto.seattlepi.com/247844

P-I reporter Lisa Stiffler can be reached at 206-448-8042 or lisastiffler@seattlepi.com. See the P-I's enviro Web page: www.seattlepi.com/environment

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