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
Peer Review Logo
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Spotted knapweed, Extension, University of Nevada, Reno, Field Guide

Learn more about the author(s)

Heidi Kratsch
Heidi Kratsch
 

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