Scotch thistle (Onopordum acanthium)

  • Scotch Thistle Plant 215x150

Category B Weed

Sunflower family (Asteraceae)

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  • Up to 12 ft. tall and branched, with spiny wings along smooth stem; covered with wooly, gray hairs


    • Alternate; oblong, 4-20 in. long, covered with wooly, gray hairs giving plant a gray-green appearance; edges (margins) are lobed or toothed with stiff spines


      • White to purple flowers, each located at the tip of a branch; base of flower is round (resembles a squashed globe), 1-2 in. wide and covered with green, purple or yellow bracts (less than 0.2 in. long), each tipped with a spine; often covered with wooly, gray hairs


        • Fleshy taproot


          • Often infests pastures, rangeland, roadsides and waste areas; known to occur in all Nevada counties

          • Biennial; reproduces by seed

          • Forms dense stands that are difficult for humans and animals to penetrate


            • Hand-removal, digging or mowing prior to flowering can be effective

            • Apply 2,4-D, dicamba, chlorsulfuron, metsulfuron or picloram to actively growing rosettes; 2,4-D + dicamba, aminopyralid, chlorsulfuron or clopyralid between rosette and late-bolt stage


              Scotch Thistle Infestation 215x150
              Scotch Thistle Plant 215x150
              Mature plant
              Scotch Thistle Flower 215x150
              Scotch Thistle Stem 215x150
              Winged stem
              Scotch Thistle Rosette 215x150
              Nevada Noxious Weed Field Guide
              Nevada Noxious Weed Guide