Hunt is on for noxious weeds in King County

Noxious Weed Program offers help to county residents in weed war

Karen Peterson, a weed specialist with King County, has been using her detective skills this past month to hunt down garlic mustard in area parks and backyards.

This elusive but dangerous forest pest gained a foothold in Seattle in the late 1990’s and employees with King County’s Noxious Weed Program have been fighting it ever since.

They’re trying to keep the weed contained in the city, and eventually get rid of it once and for all.

And they’re running out of time. Garlic mustard will start going to seed any day now, and once seeds are in the soil, they can produce plants for another decade.

A widespread and destructive weed in the Northeast and Midwestern U.S., garlic mustard is just getting going in the Pacific Northwest. To date, the weed’s presence is limited to isolated infestations in King, Clark and Skamania counties in Washington, Multnomah County, Oregon and portions of British Columbia.

“The entire Pacific Northwest is potentially at risk of invasion by this weed, which reduces native tree and shrub health by damaging the soil organisms in forests, and choking out native wildflowers and groundcover species,” said King County Noxious Weed Program Manager Steve Burke.

Peterson is stalking garlic mustard in north Seattle, where it has been found in several parks and many private yards and ravines. In one such area near Golden Gardens Park, garlic mustard infests large areas of the wooded hillsides. Peterson has been traveling door-to-door in the neighborhood to ask homeowner permission to search their backyards and the hillsides for the noxious weed.

Peterson recently received a hot tip from a Fremont resident who had seen garlic mustard in his neighborhood. Oftentimes these leads fall through, as the plant is so hard to identify, but this time the identification was accurate and Peterson attacked the new infestation before it got out of control.

Garlic mustard is one of 44 state-listed noxious weeds that the King County Noxious Weed Program is partnering with landowners to control. Noxious weeds are non-native plants introduced to Washington that cause damage to the natural or economic resources of the state.

The noxious weed program also provides workshops to interested groups and sets up weed information booths at community events.

The weed program will be demonstrating noxious weeds and answering questions at the Tukwila Backyard Wildlife Festival (http://www.backyardwildlifefair.org/ - external link) on May 10 at the Tukwila Community Center.

In June, visit the noxious weed booth at:

• Sammamish Farmers Market on June 4;
• Vashon Low Tide Festival on June 7;
• Celebrating Wildflowers at the Olympic Sculpture Park on June 8;
• Issaquah Farmers Market on June 14; and
• Kirkland Wednesday Market on June 25.

Where noxious weeds are still limited in distribution, landowners are responsible for controlling them. When one of these noxious weeds is found, the county weed program informs the responsible agency or landowner and works with them on a plan to control it before it spreads.

For the highest priority weeds, weed program staff are able to help do the control, especially when the landowner is unable to do the often strenuous work themselves.

Garlic mustard is an example of a Class A noxious weed – the highest priority for eradication – due to its potential to invade and damage forests throughout the Pacific Northwest.

“King County has a great opportunity to prevent widespread habitat degradation with a rapid, coordinated response to noxious weeds like garlic mustard,” said Burke. “By acting quickly and decisively, and coordinating with landowners and other agencies, we can succeed in preventing new invasions before they get out of control”.

Examples of other high priority noxious weeds that are still in an early phase of invasion in King County include:

• Giant Hogweed, a 10 foot tall perennial with a huge white flower head that causes burns when contact is made with its toxic juice;
• Gorse, a tall, dense shrub with long, stout spines and flowers like a Scotch broom that is a serious fire hazard due to its highly volatile oil;
• Garden Loosestrife, a yellow-flowered wetland plant has the potential to be worse than the more widely known purple loosestrife;
• Policeman’s Helmet, a pretty but highly invasive annual that rapidly takes over streamside areas; and
• Phragmites, an immense invasive grass that crowds out native wetland species.

Burke said some of the weeds that pose the highest potential threat to King County agriculture include tansy ragwort, milk thistle, meadow knapweed, goatsrue and sulfur cinquefoil. Information on all of these weeds and many others is available on the program Web site: www.kingcounty.gov/weeds.

Community groups are encouraged to contact the county weed program if they would like to schedule a presentation on noxious weeds or an information booth at their event. For more information, contact the weed program’s education specialist Sasha Shaw at 206-296-0290 or by email at sasha.shaw@kingcounty.gov.

Related Information:

Northwest Yard and Garden

King County Agriculture