Diffuse knapweed (Centaurea diffusa)

Category B Weed

Sunflower family (Asteraceae)

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  • 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


              Diffuse knapweed mature plant
              Mature Plant
              Diffuse knapweed Rosette
              Diffuse knapweed Flower
              Diffuse knapweed Leaves and stem
              Leaves and stem
              Diffuse knapweed Seedling
              Nevada Noxious Weed Field Guide
              Nevada Noxious Weed Guide