• Spotted Knapweed Plant 215x150

Category A Weed

Sunflower family (Asteraceae)

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Spotted knapweed (Centaurea biebersteinii)

    Stem

    • Up to 4 ft. tall, rough-textured, branched and bushy; NO wings on upper stems

      Leaves

      • Alternate, gray-green, up to 8 in. long; most are pinnate-divided, dotted with resin and sometimes covered with small grayish hairs; upper leaves smaller and narrower with few to no lobes

        Flower

        • White to purple, each located at the tip of a branch; base of flower is vase-shaped, 0.5 in. long, 0.3-0.5 in. wide and covered with bracts with dark, comb-like tips that give the appearance of spots (after which the weed is named)

          Root

          • Deep, stout taproot

            Other

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

            • Biennial; reproduces by seed and lateral roots

              Control

              • Mowing plants in bud to flower stage can reduce seed production; repeated hand removal can be effective; DO NOT burn
              • Several insect biological control agents are available Apply 2,4-D or dicamba in the rosette stage; apply clopyralid, picloram or aminopyralid between rosette¬†and mid-bolt stages¬†