Stem

  • Up to 2 ft. tall, highly branched and rough-textured; multiple stems can arise from woody crown; NO wings on upper stems 
Photo of squarrose knapweed stem with leaves

Leaves

  • Exist as a basal rosette prior to bolting; alternate; lower leaves pinnate-divided and 4-8 in. long; sometimes covered with short grayish hairs; upper leaves strap-like (linear) with smooth edges (margins)
Photo of small squarrose knapweed plant

Flower

  • Pink to purple, each located at the tip of a branch; base of flower is narrow vase-shaped, 0.3 in. long, 0.12 in. wide and covered with comb-like bracts; bracts tipped with a spine less than 0.12 in. long that curves outward 
Photo of squarrose knapweed plant with bright pink flower

Root

  • Deep, stout taproot
Photo of squarrose knapweed plant

Other

  • Often infests rangelands, waste areas and roadsides; known to occur in Elko and Humboldt counties 
  • Perennial; reproduces by seed
Photo of squarrose knapweed plant with small pink flowers

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

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Also of Interest:

 
Photo of diffuse knapweed with white and pink flowers
Nevada Noxious Weed Field Guide – Diffuse knapweed
Diffuse 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
Russian Knapweed Control Trial 2013-2015, Pershing County
A document of effective ways to maintain and control Russian Knapweed crops.
Foster, S., and Schultz, B. 2016, Extension, University of Nevada, Reno, PS-16-04
Paradise Valley Weed Control Demonstration Plot: Russian Knapweed
Russian knapweed is a long-lived perennial broadleaf forb. New populations typically establish from seedlings. Long-term, its spread is largely from the lateral expansion of an extensive creeping root system. Individual plants reproduce vegetatively (i.e., are clonal) and become ...
Schultz, B. 2005, University of Nevada Cooperative Extension
Managing Spotted Knapweed
Spotted knapweed is an invasive, noxious weed that should be prevented from invading lands in Nevada. It can be successfully managed over time using a variety of integrated measures if addressed in an aggressive, consistent manner using the best knowledge about control methods av...
Graham, J. and Johnson, W. 2004, University of Nevada Cooperative Extension
Russian knapweed
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
 

Associated Programs

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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.

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Master Gardeners of Washoe County

Master Gardeners provide free, research-based horticulture information to Nevadans.

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Master Gardeners of Nevada

Program trains local gardeners to provide research-based horticulture information to Nevadans