Field Guide     Weed Management     Spotted Knapweed

Spotted Knapweed (Centaurea maculosa Lam.)

Crop Impacts: Pastures

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About Spotted Knapweed:

Spotted Knapweed is a very invasive biennial perennial plant that reproduces by their seeds. It can be found throughout North America and can easily overpower native plants, altering the native biodiversity a particular area has. Once Spotted Knapweed has fully taken over an area, it releases a chemical toxin into the ground which affects and restricts the growth and germination of native plants, making them weak and easy to take over.

Family: Composite or Aster Family (Compositae)

Spotted Knapweed 2 Spotted Knapweed 3

Spotted Knapweed Scouting and Prevention:

Spotted Knapweed has a purple flower and can be found throughout North America. This weed has the ability to invade many areas such as fields, forests and disturbed areas. At full maturity, this plant will stand between 2 to 4 feet tall with a thick bed of roots. It has between 1 and 15 stems, which are rough and hairy with bluish, green oval shaped leaves that get smaller as they travel to the top of the stem. It also produces thistle-like pink to purple flowers that sit at the tip top of the bushy plant and bloom from July to September.

Spotted Knapweed Control:

The best and most efficient way to deal with Spotted Knapweed is with herbicides. Even with the use of herbicides, the weed may reinvade an area if a management plan is not followed. Here are a few herbicides that have been proven to control Spotted Knapweed:

  • - Picloram
  • - Clopyralid
  • - Clopyralid + 2,4-D
  • - Dicamba

After applying herbicide to a heavily infested area, re-seeding with perennial grasses must be done to prevent regrowth of Spotted Knapweed.

Latin / Alternative Spotted Knapweed names:

  • - Centaurea maculosa Lam.
  • - Centaurée maculée
  • - Centaurée tachetée

Additional Spotted Knapweed Resources

http://www.math.ualberta.ca/~adawson/invasive_species.html

http://www.invasiveweeds.com/canido/management/spottedknapweed.html

http://piercecountyweedboard.wsu.edu/spotted-knapweed

http://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/spottedknapweed.html