spotted knapweed

Asterales > Asteraceae > Centaurea stoebe ssp. micranthos (Gugler) Hayek

Spotted knapweed is an herbaceous biennial or perennial plant that invades open areas throughout most of the United States. Its name is derived from the black margins of the flower bract tips which give the flower heads a spotted look. A basal rosette of deeply lobed leaves is produced the first year. Rosette leaves are deeply lobed, petiolate and approximately 8 in. (20 cm) long. Flowering stems are 2/3- 4 ft. (0.2-1.2 m) tall and branched. Stem leaves are alternate and may be slightly lobed or linear. Leaves become smaller and less lobed toward the apex. Flowering occurs in the early summer. Flowers are purple to pink in color and occur on small flower heads. Spotted knapweed invades a wide variety of habitats including pastures, open forests, prairies, meadows, old fields, and disturbed areas. It displaces native vegetation and reduces the forage potential for wildlife and livestock. Spotted knapweed is native to Europe and western Asia. It was accidentally introduced into North America in contaminated alfalfa and clover seed in the late 1800s.


Identification, Biology, Control and Management Resources

  • Weeds of the Week - USDA Forest Service, Northeastern Area, Forest Health Protection

Selected Images from Invasive.org

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Plant(s);
James H. Miller, USDA Forest Service, Bugwood.org
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Infestation;
Steve Dewey, Utah State University, Bugwood.org
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Plant(s);
Steve Dewey, Utah State University, Bugwood.org
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Stand; Field 20 miles east of Missoula
Norman E. Rees, USDA Agricultural Research Service, Bugwood.org
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Plant(s); Spotted knapweed plant, Centaurea stoebe ssp. micranthos (Centaurea maculosa), in bloom.
L.L. Berry, , Bugwood.org
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Infestation; Landscape view of extensive infestations of spotted knapweed, Centaurea stoebe ssp. micranthos (Centaurea maculosa), in bloom.
L.L. Berry, , Bugwood.org
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Fruit(s);
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
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Fruit(s);
Ken Chamberlain, The Ohio State University, Bugwood.org
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Plant(s);
James H. Miller, USDA Forest Service, Bugwood.org
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Foliage;
Ohio State Weed Lab Archive, Ohio State University, Bugwood.org
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Foliage; pubescence on the underside of young leaf.
John Cardina, Ohio State University, Bugwood.org
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Foliage;
John Cardina, Ohio State University, Bugwood.org
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Seedling(s);
Ohio State Weed Lab Archive, Ohio State University, Bugwood.org
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Flower(s);
John Cardina, Ohio State University, Bugwood.org
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Flower(s);
Marisa Williams, University of Arkansas, Fayetteville, Bugwood.org
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Flower(s);
Marisa Williams, University of Arkansas, Fayetteville, Bugwood.org
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Invasive Reference(s):

Check Invasive.org for most current lists.
  • Arizona - Noxious Weed Law
  • California - Noxious Weed Law
  • Colorado - Noxious Weed Law
  • Connecticut - Noxious Weed Law
  • Kentucky - EPPC List
  • Massachusetts - Noxious Weed Law
  • Michigan - Noxious Weed Law
  • Montana - Noxious Weed Law
  • Nebraska - Noxious Weed Law
  • New Mexico - Noxious Weed Law
  • Nevada - Noxious Weed Law
  • North Dakota - Noxious Weed Law
  • Oregon - Noxious Weed Law
  • South Dakota - Noxious Weed Law
  • Tennessee - EPPC List
  • Utah - Noxious Weed Law
  • Virginia - Invasive Alien Plant Species
  • Washington - Noxious Weed Law
  • Wyonming - Noxious Weed Law
  • Mid-Atlantic - EPPC List
  • Invasive Plants: Guide to Identification and the Impacts and Control of Common North American Species
  • Invasive Plants of the Upper Midwest
  • Invasive Plant Atlas of New England
  • Midwest Invasive Plant Network


External Links


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USDA Forest Service Bugwood University of Georgia