Lewis County Priority Weeds

Some noxious weeds are of particular concern to Lewis County Noxious Weed Control due to their limited distribution or their threat to human or animal safety. Familiarize yourself with the weeds listed below and contact our office to report a sighting, or if you could use some help in determining the best way to control these weeds on your property.

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Purple loosestrife

Purple Loosestrife

Purple Loosestrife – Erect squarish stems, up to 9 feet tall, leaves 1 ½ to 4 inches long, spikes of magenta flowers 4 – 16 inches long, flowers from July to October. Spreads via rhizomes and outcompetes native vegetation that provides more adequate shelter and nesting habitat. Found in wetlands and streams in the Centralia/Chehalis area as well as Stearns Creek and Mineral Lake in Lewis County. Weed Classification: B designate


Poison hemlock

Poison Hemlock – Erect Stem, 4 – 8 feet tall with mottled purple spots, finely divided leaves, lacey white flowers in late May to August, poisonous to humans. Primarily found in urban areas, alleys, vacant lots and along rail lines in Lewis County. Weed classification: B Select

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Giant Hogweed

Giant Hogweed - – Erect Stem 1 to 3 inches in diameter and 10 to 20 feet tall with mottled purple spots, finely divided leaves , white umbrella shaped flowerheads can grow up to 2 1/2 feet in diameter, sap from stem or leaf can cause phytophotodermatitis. Primarily found in urban areas, alleys, vacant lots and along rail lines in Lewis County. Weed classification: A

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False Brome

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False Brome - grows in clumps, up to 2.5 feet tall, that stay bright green through fall. Flat, sloping leaves 5-12mm wide. Distinguishable by fine hairs on leaf margins and lower stems. Found in forests, forest edges, woodlands, riparian areas, prairies, and roadsides. Weed Classification: A


Tansy ragwort

Tansy Ragwort – Upright stems, 1 – 4 feet high, leaves alternate, clusters of yellow daisy like flowers, toxic to livestock. Grows in disturbed sites, including pastures and roadsides. Primarily found in central and western Lewis County. Weed classification: B Select

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Meadow knapweed

Meadow Knapweed – Upright stems, 20 – 40 inches tall, leaves up to 6 inches long and 1 ¼ inch wide, rose-purple flowers the size of a nickel appear in July/August. Invades moist sites including pastures, meadows, and roadsides. Found in Winlock, Vader and the Packwood area. Weed Classification: B designate

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Knotweed species


Invasive Knotweeds – Bamboo like stems that grow 4 – 8 feet tall, heart shaped leaves 4 – 6 inches long, white flowers appearing in August – September. Escaped ornamental invades riparian areas and roadsides. Found along many creeks and rivers in Lewis County, including the Cowlitz River, Tilton River and Chehalis River. Weed classification: B Select