• Squarrose Knapweed Plant 215x150

Category A Weed

Sunflower family (Asteraceae)

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Squarrose knapweed (Centaurea virgata var. squarrosa)


    • Up to 2 ft. tall, highly branched and rough-textured; multiple stems can arise from woody crown; NO wings on upper stems


      • Exist as a basal rosette prior to bolting; alternate; lower leaves pinnate-divided and 4-8 in. long; sometimes covered with short grayish hairs; upper leaves strap-like (linear) with smooth edges (margins)


        • Pink to purple, each located at the tip of a branch; base of flower is narrow vase-shaped, 0.3 in. long, 0.12 in. wide and covered with comb-like bracts, tipped with a spine (less than 0.12 in. long) that curves outward


          • Deep, stout taproot


            • Often infests rangelands, waste areas and roadsides; known to occur in Elko and White Pine counties

            • Perennial; reproduces by seed


              • 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; clopyralid, picloram or aminopyralid between rosette and mid-bolt stages