Invasive Species: Spotted Knapweed

Centaurea stoebe

Spotted knapweed is most common in central Oregon. It does have some limited presence in Yamhill County.

Why is it important to control?

Spotted knapweed is a short lived perennial that out-competes grasses and other pasture species and is difficult to control.

Purple Spotted Knapweed flowering along a roadside

How can you identify it?

Closeup image of spotted knapweed flower headCloseup image of a purple Spotted Knapweed flower
Habitat: Sunny, open locations and can be in moist soils.
Life Cycle: Short lived perennial
Height: Up to 3 ft
Leaf Description: Rosette leaves are deeply lobed. Mature leaves are pale green and hairy.
Fruit & Flower Description: Pink to purple flowers have black tipped bracts. Flowers are solitary.
Bloom Time: June to September

How do you control it?

  • Small patches can be dug up or hand pulled.

  • Dispose of plant materials in a tied plastic bag. Put the bag in the trash.

  • Herbicides effectively control meadow knapweed when used according to the label directions.

  • The Oregon Department of Agriculture has released three biocontrol agents for knapweeds.

How to Report it?

There are various ways you can report this noxious weed.

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