Stem

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

Leaves

  • 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
Photo of scotch thistle

Flower

  • White to purple flowers, each located at the tip of a branch; base of flower is round and 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
Photo of scotch thistle

Root

  • Fleshy taproot
Photo of scotch thistle

Other

  • Often infests pastures, rangeland, roadsides and waste areas; known to occur throughout Nevada
  • Biennial; reproduces by seed
  • Forms dense stands that are difficult for humans and animals to penetrate
Photo of scotch thistle

Control

  • Hand-removal, digging or mowing prior to flowering can be effective
  • Apply 2,4-D, chlorsulfuron, dicamba, metsulfuron or picloram to actively growing rosettes; aminopyralid, chlorsulfuron, clopyralid or dicamba+2,4-D between rosette and late-bolt stage; aminocyclopyrachlor pre- and post emergence
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Nevada Noxious Weed Field Guide – Scotch thistle, Extension, University of Nevada, Reno, Field Guide

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Also of Interest:

 
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Nevada Noxious Weed Field Guide – Canada thistle
Canada thistle is a noxious weed that has been identified by the state of Nevada to be harmful to agriculture, the general public, or the environment. Learn more about this weed.
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Extension, University of Nevada, Reno, Field Guide
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Nevada Noxious Weed Field Guide – Malta starthistle
Malta starthistle is a noxious weed that has been identified by the state of Nevada to be harmful to agriculture, the general public, or the environment. Learn more about this weed.
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Extension, University of Nevada, Reno, Field Guide
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Nevada Noxious Weed Field Guide – Perennial sowthistle
Perennial sowthistle is a noxious weed that has been identified by the state of Nevada to be harmful to agriculture, the general public, or the environment. Learn more about this weed.
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Extension, University of Nevada, Reno, Field Guide
Photo of purple starthistle
Nevada Noxious Weed Field Guide – Purple Starthistle
Purple starthistle is a noxious weed that has been identified by the state of Nevada to be harmful to agriculture, the general public, or the environment. Learn more about this weed.
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Extension, University of Nevada, Reno, Field Guide
Photo of yellow starthistle plant
Nevada Noxious Weed Field Guide – Yellow starthistle
Yellow starthistle is a noxious weed that has been identified by the state of Nevada to be harmful to agriculture, the general public, or the environment. Learn more about this weed.
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Extension, University of Nevada, Reno, Field Guide
 

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Integrated Pest Management

Integrated Pest Management program is a long-term management strategy that uses a combination of tactics to reduce pests to tolerable levels with potentially lower costs for the pest manager and minimal effect on the environment.