Stem

Numerous; highly branched, stiff, 1-3 ft. tall and covered with wooly gray hair; NO wings

Leaves

Alternate; mostly covered with wooly gray hair
Lower leaves 2-4 in. long with lobed to wavy edges (margins); upper leaves strap-like (linear) or lance-shaped and less than 1.2 in. long with smooth or toothed edges

Flower

Purple, pink or white, each located at the tip of a branch; base of flower is vase-shaped, 0.25-0.5 in. wide and covered with green bracts with papery or whitish edges

Root

Creeping root system; upper roots often dark brown to black

Other

Grows well on a broad range of sites; often found in rangeland, waste areas, roadsides and along waterways; known to occur throughout Nevada
Perennial; reproduces by roots and seed
Causes “chewing disease” in horses by damaging the area of the brain that controls fine motor movements, particularly of the mouth; results in starvation or dehydration

Control

Mowing and tillage are NOT effective
Apply aminocyclopyrachlor, chlorsulfuron or clopyralid from the bud to flower stage; aminopyralid or picloram from bud through dormancy; imazapic to dormant plants in fall

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

Extension Associated Contacts

Heidi Kratsch

Also of Interest:


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
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
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
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 – Russian knapweed