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).