The Enemy - Meadow knapweed (Centaurea debeauxii) is a native plant to Europe was used as a forage in Oregon in the 1950’S. This bushy perennial grows to a height of 3 feet and has deep large taproot. The leaves are free from spines, are long and narrow, and very deeply palmated. The flowers are pink to reddish purple and solitary at each end. The flowers differ from Spotted knapweed in that the bracts are tan to brown (instead of black) and they are comb like. Also the flowers are two to three times larger than Spotted or Russian knapweed. This plant has not been found in Eastern Idaho but does like to invade wet meadows, pastures, roadsides, and waste areas. This plant resembles the "big-headed knapweed” that is grown as an ornamental in many areas.
The Attack - This plant spreads like all the knapweeds – through wind dispersement. Unlike most knapweeds this one grows bushy and thick, thus crowding out desireable plants. Animals tend not to graze on the weed. All Asteracea species are terrific at taking valuable water and nutrients from the soil and can cause soil erosion when they dominate the hillsides.
The Defense - As this is a tap-rooted perennials, one can effectively control it with a shovel as long as three inches of the root are taken. Animals tend not to graze on it but I have known some sheep and possibly buffalo will seek it out for forage. Herbicides such as Milestone, Chaparral, or Tordon will work best, especially when applied when budding or in the fall after a good frost. Some of the insects that we use for the knapweed complex will also work to reduce this plant as well. If you think you have seen this nasty weed please call your local weed superintendent for positive identification.
PLEASE NOTE -The proper use and application of herbicides can be an effective way to control and eradicate noxious and invasive plants. Before using herbicides, always carefully follow the label and safety instructions on the label. While we recommend the use of herbicides as one of the effective tools for integrated pest management, the Idaho Weed Awareness Campaign assumes no liability for herbicide applications.
For more information, click on the link below to download the Idaho's Noxious Weeds Control Guidelines publication produced by the University of Idaho Extension.
U of I Idaho's Noxious Weeds Control Guidelines (183 KB PDF download)