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
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?
Brown knapweed is a perennial plant with a woody root crown that grows 20 to 48 inches tall, branching near the top.
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.
Leaves are egg-shaped or lance-shaped and undivided. Leaves become smaller moving up the stem.
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
Urophora quadrifasciata, a seed head gall fly, has been used at a few, limited brown knapweed sites in Washington.
For More Information
See our Written Findings for more information about brown knapweed (Centaurea jacea).