Weed Management Projects

Weed Eradication, Class A Noxious Weeds

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Giant hogweed, Garlic mustard, False brome

Class A noxious weeds are known to be present in Lewis County and Southwest Washington and are managed with a goal of eradication for these high priority pests. Garlic mustard, Giant hogweed, False brome and Milk thistle have moved in from neighboring areas and program staff are on the lookout for new populations of these weeds.

The massive plant, Giant hogweed has been planted in the past as an exotic ornamental and is found growing typically in home landscapes or sites where plants have been disposed. Giant hogweed is unique with it oversize height (up to 12'), flower size (15” wide) and large, dissected leaves. The plant is poisonous and requires special attention with its management.

Other Class A noxious weeds that Lewis County citizens should be aware of include: Flowering rush, Hydrilla and Slenderflower thistle.

Forest Service Invasive Plant Management


Cooperative weed management has been ongoing with the US Forest Service on the Cowlitz Valley Ranger District and Mt. St. Helens National Volcanic Monument. Weed awareness, survey, control, site restoration and monitoring are important components of this program. The major focus is managing Scotch broom, invasive knapweeds and other noxious weeds on trailheads, campgrounds and roadsides from which weed seeds can travel through the forest. Other partners in this effort include: Mt. Rainier National Park, Washington State Department of Transportation and the Noxious Weed Programs in Skamania, Cowlitz, Pierce and Yakima Counties.

WHAM - Wilderness Hay and Mulch Program

The Lewis County Weed Control Board supports the Wilderness Hay and Mulch program (WHAM) in Washington State by endorsing its use in our National Forests and construction projects. Hay growers in Lewis County can provide certified weed free hay to horseman, hunters and contractors who need this material. A current list of local WHAM producers is available at the Washington State Department of Agriculture website. The Lewis County Weed Program can provide growers with more information on the process to certify hay and straw with the WHAM standard. Additional information is available with tthe WSDA Wilderness Hay and Mulch Program.


WSDA Invasive Knotweed Control

Knotweed is an aggressive noxious weed that spreads quickly, shades out native plants and destroys wildlife habitat. Knotweed threatens riparian areas where it can survive flood events and then colonize the disturbed shorelines and adjacent uplands. The Lewis County Noxious Weed Control Board is working with the Washington State Department of Agriculture, Statewide Knotweed Program, to control invasive knotweed in the Upper Cowlitz, Upper Chehalis, South Fork Chehalis and Newaukum River Watersheds. The project works with landowners to survey, identify and control knotweed on properties adjacent to these river systems and other lands that serve as sources to spread knotweed. Funding for the project has come from the Washington State Department of Agriculture & Dept. of Natural Resources.


Knotweed Project Areas, Lewis County

Statewide Knotweed Program, WSDA

Brazilian Elodea Management


Brazilian elodea is being managed at Plummer Lake, in Centralia where the infestation most likely got started from the disposal of an aquarium. The management goal is eradication of the plant within the lake. The control strategies have been adaptive over the years to reduce this noxious weed. Funding for the project has come from the Washington State Department of Ecology.