Invasive Plant

Spotted Knapweed

Centaurea stoebe
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Warning

Contact with Spotted knapweed can cause skin irritation. Hands and exposed skin should be washed with soap and water following contact with this plant.

About This Species

Spotted knapweed is a prolific seed producer, with individual plants producing up to 140,000 seeds per square metre. Seeds and plant fragments make their way into hay and the undercarriages of vehicles, allowing for new infestations over great distances. Both knapweeds spread by wind, livestock, and people, preferring open areas and well-drained soils where they establish in grasslands, open forests, and along roadsides. Spotted and Diffuse knapweed are able to spread over large areas because of a secret weapon — an ability to release a chemical that kills surrounding plants. They choke out desirable forage for livestock and wildlife and increase soil erosion.

How to Identify

Spotted knapweed grows with several branched
stems growing vertically from a thick taproot. Leaves
become smaller as they advance up the stem Flowers are purple, sometimes white, found individually,(not in clusters), at the ends of branches. Black-tipped flower
head bracts (leaf-like petals) give plants a spotted appearance. Spotted knapweed can grow to 1.5 m in height.

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Spotted knapweed is a PlantWise "Alert" species - Gardeners should avoid purchasing or planting.

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