Where does it grow?

Spotted knapweed is found in dry meadows, pastures, rocky areas, gravel mines, roadside, railroads, airports, vacant lots, hayfields, forest clearings and on the sandy or gravelly floodplains of streams and rivers. 

• In northeastern Washington, the species occurs on glacial till and outwash soils, where it has been found up to 6500 feet.

• In central Washington, spotted knapweed often occurs in association with irrigation.

What is the distribution in Washington State?

Click on map to enlarge.

• Spotted knapweed has been documented in several counties throughout Washington, refer to map for distribution levels in specific counties.
• If you think you may have seen this weed, please contact your county weed coordinator or us at noxiousweeds@agr.wa.gov.

• Distribution map is based on 2003 data

How do I control it?

General control methods: Control methods must be repeated to be effective.

Cultural: Seasonal grazing

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

Mechanical: Seasonal mowing, tillage

Biological: Ten biocontrol agents that have been released on spotted knapweed in Washington:

• Agapeta zoegana (root-boring moth)
• Bangasternus fausti (seed headweevil)
• Chaetorellia acrolophi (seed head fly)
• Cyphocleonus achates (root-boring/gall weevil),
• Larinus obtusus (seed head weevil), Terellia virens (seed head fly) are not presently collectable, and
  their effectiveness is unknown.
• Larinus minutus (seed head weevil) is available in limited quantities
  for redistribution.
• Metzeria paucipunctella (seed head moth), Urophora affinis (seed head gall fly), and Urophora quadrifasciata (seed head gall fly) are available for mass collections.

Are there plants that may be confused with Spotted knapweed?

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.

For more information