Priority: - Eradicate
Tags: Agricultural | Biocontrol
Identification and Reproduction
- 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.
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
- 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.
- Out-compete native vegetation.
Prevention is a high priority for this plant.
- Digging or hand-pulling may be effective if entire root systems are removed.
- Avoid mowing as this will disperse stem fragments and stimulate regrowth.
- 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.
- 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.
For more details check out the Invasive Species Compendium datasheet on Centaurea debeauxii (meadow knapweed).
Header photo (Doug Murphy).