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Meadow knapweed

Meadow knapweed

Meadow knapweed

(Centaurea pratensis Centaurea pratensis)

Priority: -  Eradicate

Tags: Agricultural | Biocontrol

Identification and Reproduction

Identification: 

  • Meadow knapweed is a hybrid species between black knapweed (C. nigra) and brown knapweed (C. jacea). Therefore, its characteristics will have a variable range. 
  • Its stem grows up right and can be slightly branched. It can grow from 30 to 150 cm in height. 

  • It grows from a taproot and will develop a woody crown. 
  • Leaves are oblanceolate growing from a leaf stalk that attaches to the stem. Moving up the stem leaves will decrease in size and lose its stalk. 
  • Flowers occur at the end of stems. They range from purple to pink, rarely white. Flowers are showy and broad.
  • Flowerheads are the size of a nickel and will be encased by bracts that are evenly fringed and brown in colour. When mature the bracts will appear papery gold. 

Reproduction: 

This plant primarily reproduces by seed but will also regrow from stem and root fragments. 

Habitat & Ecology

This plant grows in a variety of habitats, ranging from pastures, meadows, roadsides, riparian areas, forest edges, clearcuts and industrial sites

Impacts

Social: 

  • Seeds can contaminate agricultural seed crops. 
  • Infestations can suppress the growth of crops and forage availability for livestock. 
  • Can minimize silvicultural reforestation efforts on forest lands and plantations. 

Ecological: 

  • Out-compete native vegetation.

Management

Prevention is a high priority for this plant. 

Mechanical/Manual Control: 

  • Digging or hand-pulling may be effective if entire root systems are removed. 
  • Avoid mowing as this will disperse stem fragments and stimulate regrowth. 

Chemical Control: 

  • Selective broadleaf herbicides such as aminopyralid and clopyralid are the most effective. It is suggested to use herbicides on larger infestations. 
  • For optimal treatment usage, apply when plants are transitioning from rosette to bolting stage. 
  • Please carefully read labels prior to application. 

Biological Control: 

  • Like many knapweed species, meadow knapweed has seen success with some bio-controls. 
  • There has been some success with a fly, weevil and a moth that help suppress plant growth. 

Resources

For more details check out the Invasive Species Compendium datasheet on Centaurea debeauxii (meadow knapweed). 

Header photo (Doug Murphy).