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
 

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