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Invasive Species: Spotted Knapweed

Invasive Species: Spotted Knapweed

 

Spotted Knapweed

(Centaurea stoebe)
*Established in Michigan*

Report this species:

Use the Midwest Invasive Species Information Network (MISIN) online reporting tool

- Or - download the MISIN smartphone app and report from your phone - MISIN.MSU.edu/tools/apps/#home

 

A spotted knapweed plant grows in gravel near a fence post.

Photo courtesy of Michael Shephard, USDA Forest Service, Bugwood.org. 

Pinkish-purple spotted knapweed flowers.

Photo courtesy of Rob Routledge, Sault College, Bugwood.org.

A spotted knapweed rosette growing close to the ground.

Photo courtesy of Rob Routledge, Sault College, Bugwood.org.

Identification:

  • An herbaceous, bushy, perennial plant growing 2-3 feet.
  • Elongated, bluish- or grayish-green leaves divided into lance-shaped lobes. 
  • Pinkish-purple flowers are thistle-like and bloom from July through September.
  • Long, stout tap-root can send shoots to start new plants.
  • Seeds are carried on fine, white tufts emerging from the flower base.

Habitat: Often found in open fields or scrub-shrub areas with poor soils or sands and also in disturbed areas, hay fields and pastures.

Native Range: Eurasia.

U. S. Distribution:  Throughout most of the U.S. and Canada.

Local Concern: Spotted knapweed is poisonous to other plants, creating barren areas where only knapweed grows. It is a threat to pastures and dry ecosystems including prairies and dunes. Can be a skin irritant.

MORE INFORMATION:

Spotted Knapweed Invasive Species Alert - Printable PDF