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

Stem

Up to 4 ft. tall, rough-textured, branched and bushy; NO wings on upper stems

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

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)

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

Authors of this scholarly work are no longer available.

Please contact Extension's Communication Team for assistance.

Also of Interest:


A Guide to Desert Bioscape This publication will help the reader understand how to garden more efficiently in the Mojave Desert and in other dry areas. Beautiful yards and landscapes can be created while applying environmentally friendly principles. Putting these principles into use will help conserve wate... Robinson, M.L., Johnson, W.S., Post, R.L., and Carlos, W.J. 2004, Extension, University of Nevada, Reno, SP-04-12
Scouting the Landscape Good pest management in the landscape begins with a good scouting program. Scouting what is actually happening to the plants in the landscape. Rather just spraying pesticides, scouting allows the gardener to properly identify problems first. Appropriate solutions can be determin... Robinson, M.L., Johnson, W. S., Post, R. L., Carlos, B. 2000, Extension: University of Nevada, Reno, SP-00-02
Using Pesticides Safely Whether one is a commercial pesticide applicator or homeowner safely spraying a few pests in their yard safety is a priority. This publication highlights safety practices that will help the pesticide applicator manage pest problems without contaminating the environment or causing... Johnson, W.S., Post, R., Carlos, W., Post, E., and Robinson, M.L. 2000, Extension, University of Nevada Reno, FS-00-19

Nevada Noxious Weed Field Guide – Spotted knapweed