Eradication of meadow knapweed in Minnesota is no longer possible however, there is still a pressing need to contain it 



department of agriculture


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September 4, 2024

September Weed of the Month: Meadow Knapweed Noxious Weed Status Change

Eradication of meadow knapweed in Minnesota is no longer possible however, there is still a pressing need to contain it 

"*Julia Dellick, Minnesota Department of Agriculture*"

Meadow knapweed ("Centaurea jacea x nigra") poses a significant threat to various pastures, hayfields, meadows, riparian areas, forest margins, and rights-of-way, where it can easily outcompete native plants. This aggressive behavior leads to diminished forage availability, compromised wildlife habitat, and a decline in species diversity. There is also a risk of hybridization with spotted knapweed, which could make it even more difficult to control.

Because of the severity and number of problems caused by meadow knapweed, it was initially classified on the Noxious Weed List as a Prohibited Eradicate species. All plants had to be destroyed with the goal to eliminate it in Minnesota. Recently, due to an increased number of infestations across Minnesota and the inability to no longer eradicate the weed, it has been moved to the Prohibited Control list.  

For Prohibited Control species, efforts must be made to prevent seed maturation and dispersal of the plants into new areas. Transportation (unless permitted by the county or state), propagation, or sale of these plants are prohibited in Minnesota. Failure to comply may result in enforcement action by the county or local municipality. 

Purple flowers on meadow knapweed [ [link removed] ]

Flowers are pink to purple and approximately ¾ inch in diameter.

*Download pho**to* [ [link removed] ]

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Meadow knapweed is a sturdy perennial plant with lance-shaped leaves and upright, red-tinted stems. It can grow 20-40 inches in height. Its branches have single pink or purple flowers that occasionally appear white with a diameter of approximately ¾ inch. As summer shifts to fall, these flowers give way to white or light brown seeds with short plumes. Young leaves and flower buds have a cobweb-like texture, and seedlings have taproots, while mature plants feature a cluster of roots beneath the crown. Meadow knapweed and spotted knapweed are closely related. However, spotted knapweed has grey-green colored foliage with deeper lobes.

Meadow knapweed leaf lobed 4-9 inches long [ [link removed] ]

Leaves are occasionally lobed and can be 4-9 inches long.

*Download photo [ [link removed] ]*

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Controlling small infestations of meadow knapweed can be done through a combination of hand-pulling and digging. Hand-pulling is more effective on seedlings as they have single tap roots, while clusters of mature plants are nearly impossible to hand-pull and must be dug. The entire root cluster must be removed to prevent regrowth. If the plants have flowers and/or seedheads, be sure to bag and dispose carefully to prevent spreading seed. Herbicides are another effective management tool for meadow knapweed. For specific herbicide recommendations, contact your local University of Minnesota Extension agent, co-op, or certified landscape care expert for assistance and recommendations.

Mowing is not a recommended method as it does not control meadow knapweed and may further spread seed. Biological control is not an effective control option for meadow knapweed. To prevent the spread of meadow knapweed, always be sure to clean equipment, vehicles, and footwear before leaving an infested area. For all management options, infestation sites will need to be monitored and treated repeatedly until the seedbanks are depleted.

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*MEDIA:* For more information on Weed of the Month, contact Brittany Raveill, MDA Communications, at [email protected] or 651-201-6131






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