Stem

  • Up to 4 ft. tall, rough-textured, branched and bushy; NO wings on upper stems
Photo of spotted knapweed stem with leaves

Leaves

  • Alternate, gray-green, up to 8 in. long; most are pinnate-divided, dotted with resin and sometimes covered with small grayish hairs; upper leaves smaller and narrower with few to no lobes
Photo of spotted knapweed plant

Flower

  • White to purple, each located at the tip of a branch; base of flower is vase-shaped, 0.5 in. long, 0.3-0.5 in. wide and covered with bracts with dark, comb-like tips that give the appearance of spots (after which the weed is named)
Photo of spotted knapweed pink flower

Root

  • Deep, stout taproot
Photo of spotted knapweed plant in a field of dry grass

Other

  • Grows best on dry, well-drained soils; often infests rangelands, waste areas and roadsides; known to occur throughout Nevada
  • Biennial; reproduces by seed and lateral roots
Photo of a field with spotted knapweed plants

Control

  • 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 glyphosate rosette to bolt stage; aminocyclopyrachlor, aminopyralid, clopyralid, or picloram preemergence to bolt stage
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Nevada Noxious Weed Field Guide – Spotted knapweed, Extension, University of Nevada, Reno, Field Guide

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Also of Interest:

 
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Nevada Noxious Weed Field Guide – Squarrose knapweed
Squarrose knapweed 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 – Russian knapweed
Russian knapweed 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
Nevada’s Priority Agricultural Weeds: Russian Knapweed
Russian knapweed (Acroptilon repens) is a non-native perennial forb (wild flower) that arrived in the United States in the late 1890s. This weed is well adapted, growing in damp to poorly drained soils with high salinity and/or alkalinity.
B. Schultz, S. Foster 2021, Extension, University of Nevada, Reno, SP-21-02
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Nevada Noxious Weed Field Guide – Mediterranean desert knapweed
Mediterranean desert knapweed 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
Managing Russian Knapweed
This fact sheet contains several ways to manage Russian Knapweed by understanding the habitat, identification, threat, and many more.
Graham, J. and Johnson, W. 2004, Extension | University of Nevada, Reno, FS-04-37
 

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