Meadow Knapweed
Centaurea x moncktonii
Washington State Classification
Class B — Control Required (Designated)
Meadow knapweed is an aggressive invasive species that spreads into pastures and meadows.
Required control in Region 1 (all western Washington counties)
Quick Reference
Identification
Growth Habit
As a hybrid between brown knapweed and black knapweed (Centaurea jacea and Centaurea nigra, and possibly Centaurea nigrescens), meadow knapweed can have variable characteristics between the parent plants. It is a perennial that typically grows between 1 and 5 feet tall.
Leaves
Leaves not divided, up to 6 inches long and 1.25 inches wide with smooth or slightly lobed or toothed margins. Leaves decrease in size up the stem.
Flowers
Flower heads are solitary and terminal on branch tips. Bracts at the base of flower heads are light to dark brown and have papery, fringed margins. Bracts have a metallic gold sheen when plants are flowering. Flowers are rose purple to white.
Fruit & Seeds
Seeds are white to light brown in color and may have a short row of hairs on one end.
Impact
Meadow knapweed is an aggressive invasive species that spreads into pastures and meadows. It outcompetes desirable forage plants as well as other native plants species.
Ecology & Spread
Habitat
Meadow knapweed occurs in mesic meadows and pastures, forest openings, roadsides, waste areas and floodplains of rivers and streams. Please click here to see a county level distribution map of meadow knapweed in Washington.
Spread Mechanisms
Reproduction
Meadow knapweed reproduces from seed and also can respout from root crowns.
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Control Methods
Biological Control
- The blunt knapweed flower weevil, Larinus obtusus, is most destructive in the larval stage by its feeding on seeds within the flowerheads. The adults also cause damage by feeding on meadow knapweed leaves. For more information about the biological control of meadow knapweed, please visit WSU Extension Integrated Weed Control Project.