Brown Knapweed

Centaurea jacea

   

Family: Asteraceae

Other common names: rayed knapweed

Weed Class: B

Year Listed: 1988

Native to: Europe and Western Asia

Toxic: not known to be

additional photos

 

   

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.

How does it reproduce?

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

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 do I control it?

General Control Strategy

.

Mechanical Control

.

Cultural Control

.

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

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

Additional Photos


 
 

Brown knapweed flower

    

back to page top