Common names: meadow knapweed
Scientific names: Centaurea x moncktonii, C. jacea x nigra, C. pratensis Thuill, and C. debauxii subsp. thuilleri.
Related species: Other knapweeds and hybrids including spotted knapweed, Centaurea stoebe L. ssp. micranthos (Gugler)
Meadow knapweed is native to Europe and is likely a fertile hybrid between black (C. nigra L.) and brown (C. jacea L.) knapweeds. It may have been introduced to western North America for forage, but it is not palatable and has low nutritional. Meadow knapweed escaped cultivation and is proliferating rapidly in the Pacific Northwest. Few meadow knapweed populations have been detected in Minnesota so it would be advantageous to control these populations before they have an opportunity to spread.
Meadow knapweed is a perennial plant that has multiple upright, reddish stems that are 20-40” tall. Single flowers, mostly pink/purple but occasionally white, are at the ends of branches and are approximately ¾” in diameter. Flowering occurs mid-summer until fall followed by the production of white to light brown seeds with short plumes. Leaves are lance shaped and pubescent, occasionally with wavy margins or lobed. Basal leaves grow up to 4” long. Seedlings are tap-rooted and mature plants develop a cluster of roots below the crown.
Spotted knapweed is a similar species that is common in Minnesota. The two knapweed species are easily distinguished by the leaf shape and color. Spotted knapweed leaves are grey-green and are more deeply lobed. Distinguishing meadow knapweed from spotted knapweed.
Meadow knapweed prefers sunny and wet conditions such as wet meadows, hayfields, pastures, riparian areas, roadsides, and forest openings.
Seed is the predominant means of reproduction although meadow knapweed can also be propagated by root crown fragments. Seed can be dispersed by wind, water, vehicles, and with hay. Meadow knapweed occurs in Colorado, Oregon, Idaho, and Washington in the United States and British Columbia, Ontario, and Quebec in Canada. It has very limited distribution in northern Minnesota with infestations reported in St. Louis and Koochiching Counties.
Meadow knapweed can overtake other plants in pastures, hayfields, meadows, riparian areas, forest margins, and rights-of-way. This can result in reduced forage, wildlife habitat, and species diversity. A similar weed species, spotted knapweed, is abundant and can hybridize with meadow knapweed if the species co-exist. Concerns about a resulting vigorous hybrid add to the rational for meadow knapweed eradication in Minnesota.
To prevent the introduction of additional meadow knapweed, clean equipment, vehicles, and footwear before transporting to Minnesota from meadow knapweed infested areas.
For all management options, infestation sites will need to be monitored and treated repeatedly until the seedbanks are depleted.
Meadow knapweed is a prohibited noxious weed on the eradicate list. This means that all of the above and below ground parts of the plant must be destroyed, as required by Minnesota Statutes, Section 18.78. Additionally, no transportation, propagation, or sale of these plants is allowed.
Additional images, fact sheets, and best management practices at:
Minnesota Department of Agriculture (MDA), 625 Robert Street N, St. Paul, MN 55155-2538, email@example.com