• Diffuse Knapweed Plant 215x150

Category B Weed

Sunflower family (Asteraceae)

Helpful Links

List of all Photo Credits

Diffuse knapweed (Centaurea diffusa)

    Stem

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

      Leaves

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

        Flower

        • 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

          Root

          • Deep, stout taproot

            Other

            • 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

              Control

              • 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