Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Nevada Noxious Weed Field Guide – Canada thistle, Extension, University of Nevada, Reno, Field Guide

Stem

  • Up to 4 ft. tall, green to brown, branched at the top and usually lacks hair (glabrous)
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Leaves

  • Alternate, oblong or lance-shaped, 2-8 in. long, shiny and lack hair; NO leaf stems (petioles); leaf edges (margins) are wavy, lobed or toothed with spiny edges
Photo of canada thistle
Canada thistle rosette

Flower

  • Pink, purple or white; occur in clusters at the ends of branches; base of flower is vase-shaped, 0.5-0.75 in. wide, lacks prickles and is covered with green to purple bracts with dark tips
Photo of canada thistle flowers
Canada thistle flowers

Root

  • Deep, extensive creeping root system
Photo of canada thistle plant
 

Other

  • Grows best in moist areas; often found in pastures, hay fields, waste areas and along waterways; known to occur throughout Nevada
  • Perennial; reproduces by both roots and seed; plants often appear in patches or colonies due to the spreading root system
Photo of canada thistle

Control

  • Repeated mowing, tillage, cutting or hand removal prior to seed production can provide suppression
  • Several biological control agents are available
  • Apply aminocycloprachlor, aminopyralid, chlorsulfuron, clopyralid or picloram pre- or post emergence; repeated applications of 2,4-D, dicamba or glyphosate to actively growing plants

Learn more about the author(s)

Heidi Kratsch
Heidi Kratsch
 

Also of Interest:

 
Photo of canada thistle plant.
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