A fight to break knotweeds hold in Pierce County
When it comes to invasive weeds, it’s best to pick your battles. At least that’s the rationale of Sean MacDougall, who last year embarked on what he envisions as a five-year campaign against one of the most notorious: Japanese knotweed.
MacDougall knew a lot about knotweed before he became program coordinator of the Pierce County Noxious Weed Control Board.
What Scotch broom is to sunny roadsides and abandoned building lots, knotweed is to wetlands and river systems, MacDougall said.
“It loves to have its feet wet,” he said.
Knotweed’s bamboo-like stalks and spreading underground stems crowd out young willows, alders and cottonwoods, along with shrubs that otherwise might cling to the river shore. By doing so, knotweed destroys fish and wildlife habitat and contributes to erosion, experts say.
Originally imported from Asia as an ornamental in the 19th century, knotweed is widely dispersed now.
“The Puyallup River’s got a lot. It’s pretty scary,” MacDougall said.
Knotweed also causes problems in Tacoma, along Commencement Bay, and elsewhere in Washington, as well as in Alaska, Canada, Britain and other countries. And like Scotch broom, knotweed defies restraint. “It’ll buckle pavement,” MacDougall said.
Still, he said, he was looking for a way to make a difference when he took over the tiny weed control board in December 2006. The agency is perhaps best known to rural residents as the tansy ragwort police – for the seasonal spotters who drive around looking for weeds that poison cattle and ruin hay.
“Any landowner is capable of removing tansy ragwort from his property,” MacDougall said of the tall yellow flowers, easily yanked out. In Japanese knotweed, MacDougall found a more elusive foe.
With the encouragement of the Nisqually Tribe and $75,000 in federal and state grants, he and a couple of newly hired eradication experts focused in on the Nisqually River.
The effort is not unique to Pierce County. This year, the state Department of Agriculture is providing $650,000 to 22 groups in 26 Washington counties, including some in Eastern Washington. The agency is targeting four types of knotweed, said control coordinator Marshall Udo, because the plant typically spreads from stem fragments that float downstream.
MacDougall selected the Nisqually as a manageable target in part because of its importance to salmon, which inhabit the river and its tributaries downriver of Tacoma Power’s Nisqually hydropower project at La Grande.
Biologists working for the Nisqually Tribe who have floated the lower river knew some knotweed had taken hold, and suspected the problem could become worse if no one tried to contain a more serious infestation just outside Mount Rainier National Park.
Now, in the second year of the project, MacDougall said his team of weed killers – with help from the tribe, the park, Tacoma Power, the U.S. Fish & Wildlife Service, Fort Lewis and others – have surveyed the length of the river and initiated the assault.
“We’ve just kind of begun this battle,” said Bret Forrester, a Tacoma Power wildlife biologist. “It takes a coordinated effort. It’s not an easy plant to kill.” Tacoma Power alone has treated several knotweed-plagued acres near La Grande.
While knotweed infests perhaps 1,000 acres in the river’s upper watershed, between Mount Rainier National Park and Alder Lake, it is less of a threat downriver, MacDougall said.
Last year, the weed control crew applied herbicide to 80 patches of knotweed encountered at locations along the lower 38 miles of the river. About 31/2 acres of land was involved.
To kill knotweed, weed control workers spray and inject glyphosate, the herbicide sometimes sold under the trade name Roundup. Often, more than one application is necessary, MacDougall said.
Eradication efforts along the upper Nisqually River, beginning just outside the national park, began earlier this year. So far, MacDougall said, the crew has treated about 45 acres along a couple of miles of river between the park and Copper Creek, site of a popular restaurant on Highway 706 near Ashford. Between 25 and 30 property owners have been involved.
Phil Freeman, who with his wife, Catharine Gallagher, bought Copper Creek Inn in 2001, said he’s happy to have help battling knotweed. The couple tried to dig it up, but the plant is relentless, he said. “This is a tough cookie we’re dealing with,” he said.
Elsewhere, others have been inspired by the Pierce County weed board effort.
Pierce County recently received a $10,000 state Department of Natural Resources grant to initiate knotweed control in the Chambers Creek canyon area, including Chambers, Leach, Peach and Flett creeks, said Bob Vogel, who works for Pierce County public works and utilities. Affected property owners will be notified, he said.
Jeanine Riss, of Tacoma’s Citizens for a Healthy Bay, said her volunteers have learned from MacDougall. One eradication technique the group has used is to cover the roots of knotweed with black plastic or special fabric. That helps kill the plant by drying it out.
Perhaps the most essential tool is persistence, MacDougall said: “It could take a least three to seven years to eradicate a knotweed patch.”
Susan Gordon: 253-597-8756
