King County’s noxious weed list growing

Weed board now requires knotweed control on upper, middle Green River

King County noxious weed specialists are on high alert to find three new Class A noxious weeds that are trying to take root here.

Shiny geranium and false brome are moving up from Oregon, while flowering-rush is on the march south from Canada and west from the Great Lakes region.

All three weeds are Eurasian species that pose a high risk to natural resources and native habitats, and they’re hard to stop once they get established.

“Fortunately, these particular invasive plants have only been found in a few places in the state, and are not in King County yet,” said Steve Burke, manager of King County’s Noxious Weed Program. “We have the perfect opportunity to prevent these invasives from establishing themselves here.”

Burke said the King County Noxious Weed Board added these three species to the county’s Class A noxious weed list at a recent hearing.

False brome and shiny geranium pose risks to woodland habitats and are becoming alarmingly widespread in the Willamette Valley in Oregon. Both have been found in southwest Washington and shiny geranium has also been found in a state park in Skagit County.

County weed specialists will focus their search for these species in parks and along roadsides, since this is where the weeds have shown up elsewhere in the state.

Flowering-rush is found on Silver Lake in Whatcom County and on the Yakima River. The hunt for this plant will focus on lakes and river shorelines. The plant could also show up in ponds and water gardens, as it has been used as an ornamental.

“There is information on the new Class A’s and other noxious weeds on our Web site, and county residents can help us by reporting any suspected noxious weeds to us right away,” said Sasha Shaw, education specialist for the King County Noxious Weed Program.

Other changes made to the county noxious weed list include upgrading the status of invasive blackberry species to the Class C noxious weed list and designating an area of the Green River where landowners are required to control invasive knotweed species.

Himalayan and evergreen blackberry were already considered invasive vegetation according to the county noxious weed list, but now they have been formally classified by the State Weed Board as noxious weeds in Washington state.

This will change the way blackberry is treated in some regulations such as the county’s Clearing and Grading Ordinance, which allows for exceptions for noxious weed control if the county’s best management practices are followed.

Control of blackberry is still not required in King County, but landowners can contact the noxious weed program for information on recommended control methods.

Invasive knotweed is a widespread problem in King County and control is recommended but not required for public agencies and private landowners.

However, according to Burke, the county has led a comprehensive knotweed control program on the upper and middle Green River for the past five years and has significantly reduced the problem there to a manageable level.

Starting this year, public and private landowners will be responsible for controlling knotweed on the banks of the upper and middle Green River and its tributaries upstream of Auburn.

“We expect to receive enough grant funding this year to continue doing much of the knotweed control work, but landowners will have to make sure knotweed is controlled on their property, and to cooperate with the county if they would like assistance,” Burke said.

To help protect the state’s resources, the Washington State Noxious Weed Control Board adopts a statewide noxious weed list each year.  Each county’s weed board then adopts a county noxious weed list that establishes which weeds require control by property owners and public agencies.  The King County Noxious Weed Board met Jan. 21 to formally approve the county weed list for 2009.

The county is required to include all state-listed Class A weeds and any Class B weeds designated for the county by the state, and may select additional state-listed weeds for required control in the county.

The county’s noxious weed list places a priority on preventing new infestations of the most serious noxious weeds, and encourages property owners to work together in stopping the spread of established noxious weeds.

Information on the county noxious weed list and state noxious weed law can be found online at www.kingcounty.gov/weeds.

For more information on the King County Noxious Weed Board and the county weed program, call or e-mail Burke for more information at 206-205-6927 or steven-j.burke@kingcounty.gov.

Related Information

Noxious Weeds

King County Water and Land Resources Division