• Diffuse Knapweed Plant 215x150

Category B Weed

Sunflower family (Asteraceae)

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Diffuse knapweed (Centaurea diffusa)


    • Up to 2 ft. tall; rough-textured; highly branched; bushy; covered with short, stiff hairs; NO wings on upper stems


      • Alternate, lower leaves pinnate-divided, 4-8 in. long; sometimes covered with short grayish hairs; upper leaves strap-like (linear) with smooth edges (margins)


        • White to sometimes purple, each located at the tip of a branch; base of flower is vase-shaped, 0.5 in. long, 0.12 in. wide and covered with yellow, comb-like bracts tipped with a narrow spine


          • Deep, stout taproot


            • Grows best in dry, well-drained soils; often infests rangelands, waste areas and roadsides; known to occur in Churchill, Clark, Douglas, Elko, Eureka, Lander, Lincoln, Nye, Washoe and White Pine counties

            • Biennial, but sometimes annual or perennial; reproduces by seed; dry, mature plants often break off and tumble in the wind to spread seed


              • Mowing plants in bud to flower stage can reduce seed production; repeated hand removal can be effective; burning is NOT effective

              • Several insect biological control agents are available

              • Apply 2,4-D or dicamba in the rosette stage; apply clopyralid, picloram or aminopyralid between rosette andmid-bolt stages