Brown Knapweed

Centaurea jacea

Brown Knapweed

Family: Asteraceae

Other Common Names: rayed knapweed
Weed class: B
Year Listed: 1988
Native to: Europe and Western Asia
Is this Weed Toxic?:

not known to be


Legal listings:

WA Quarantine list, WAC 16-750

Why Is It a Noxious Weed?

Knapweed invasions have many impacts including an increase in production costs for ranchers, degrading wildlife habitat, crowding out desirable forage, decreasing plant diversity, increasing soil erosion rates, and posing wildfire hazards.

How would I identify it?

General Description

Brown knapweed is a perennial plant with a woody root crown that grows 20 to 48 inches tall, branching near the top.

Flower Description

Flowers are rose to purple and rarely white. Flower heads are ¾ to 1 inch, light to dark brown. Hairy bracts at base of flower heads are wider at the tips. They have broad, thin, papery margins. The center of each bract is dark brown.

Leaf description

Leaves are egg-shaped or lance-shaped and undivided. Leaves become smaller moving up the stem.

Stem description

Stems may be single to a few for each plant, upright and branched near the top and somewhat hairy.

Fruit Seed Description

Seeds are tan, small with fine hairs and no pappus.

May Be Confused With

Many species of Centaurea look very similar to each other, making identification difficult. If you need help with plant identification, please contact your county noxious weed coordinator.

Where does it grow?

Brown knapweed grows on roadsides and in meadows, pastures and open areas. Please click here to see a county level distribution map of brown knapweed in Washington.

How Does it Reproduce?

Brown knapweed reproduces by seed and can regenerate from the crown.

How Do I Control It?

General Control Strategy

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Mechanical Control

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Cultural Control

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Biological Control

Urophora quadrifasciata, a seed head gall fly, has been used at a few, limited brown knapweed sites in Washington.

Herbicide Control

Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.

For More Information

Selected Knapweeds of Washington Brochure

See our Written Findings for more information about brown knapweed (Centaurea jacea).

Whatcom County NWCB Control Options for Knapweeds

Additional Photos