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Brown Knapweed (Centaurea jacea L.) Family: Family: Asteraceae (Compositae) Description and VariationDescription and Variation: Brown knapweed is a perennial plant with a woody root crown that grows 20 to 48 inches tall, branching near the top. The branches have egg-shaped or lance-shaped undivided leaves that become progressively smaller up the stem. The stem is ridged and sometimes purple-striped. The 3/4-to-one inch, light to dark brown heads are found at the ends of the branches. The somewhat hairy bracts are wider at the tips with broad, thin, papery margins. The center of the bracts is dark brown. The bract tips overlap the base of nearby bracts. The flowers, which bloom from July to October, are rose to purple but rarely white. Economic ImportanceEconomic Importance: As with other knapweed species, brown knapweed has shown itself to be aggressive and invasive. This one is particularly so in meadows and pastures, crowding out more desirable forage. Geographical Distribution: Brown knapweed is native to southern Scandinavia, Atlantic and Central Europe, northern Italy, and the Balkans. HabitatHabitat: Brown knapweed grows in
grasslands and in open woods over most of Europe or Eurasia and occurs at elevations up to
6,600 feet in mountainous areas of central Europe to 63° 43' north latitude. HistoryHistory: Centaurea jacea has been grown both as an ornamental garden plant and as a crop. It was also introduced at seaports as a contaminant. It was present in meadows at Cedar Hills, Victoria, Vancouver Island, in 1887. In Washington, brown knapweed occurs mainly west of the Cascades. Growth and DevelopmentGrowth and Development: Brown knapweed is a perennial plant. ReproductionReproduction: Brown knapweed reproduces from seeds and from the woody root crown. HybridsHybrids: Centaurea jacea is a parent to meadow knapweed (Centaurea jacea x nigra). Response to HerbicidesResponse to Herbicides: Glyphosate, picloram, 2,4-D, and clopyralid have all been used on knapweeds. Please refer to most recent Pacific Northwest Weed Control Handbook for more information. Read and follow current herbicide labels and recommendations for control. Response to Cultural Methods: Not known. Biocontrol PotentialsBiocontrol Potentials: Urophora quadrifasciata, a seed head gall fly, has been used at a few limited brown knapweed sites in Washington. References: Frankton and Mulligan. 1970. Weeds of Canada. Canada Dept. of Agriculture. Moore and Frankton. 1974. The Thistles of Canada. Monograph 10. Canada Dept. of Agriculture. Muenscher, W.C. 1955. Weeds, 2nd ed. Cornell University Press, Ithaca, NY. Roche', B.F. Jr., G.L. Piper, and C.J. Talbott. 1986. Knapweeds of Washington. EB 1393. Extension Bulletin. W.S.U. Cooperative Extension, Pullman. Roche', B.F. Jr., G.L. Piper and C.J. Talbott. 1986. The Collection History of Centaureas Found in Washington State. Research Bulletin XB 0978. Agricultural Research Center. Washington State University, Pullman.
This page was last updated 03/31/07 |
In Russia, it grows in meadows, woodland clearings,
and in cutover areas of forest. The species can tolerate partial shade. In Romania, brown
knapweed grows in pastures, orchards, and plains, but it prefers the mountainous regions.
