Stem

Up to 2 ft. tall; rough-textured; highly branched; bushy; covered with short, stiff hairs; NO wings on upper stems

Leaves

Alternate, lower leaves pinnate-divided, 4-8 in. long; sometimes covered with short grayish hairs; upper leaves strap-like (linear) with smooth edges (margins)

Flower

White to pale purple, located at the tip of a branch; base of flower is vase-shaped, 0.5 in. long, 0.12 in. wide and covered with yellow, comb-like bracts tipped with a narrow spine

Root

Deep, stout taproot

Other

Grows best in dry, well-drained soils; often infests rangelands, waste areas and roadsides; known to occur in Douglas, Elko, Eureka, Lander, Lincoln, Nye, Washoe and White Pine counties
Biennial, but sometimes annual or perennial; reproduces by seed; dry, mature plants often break off and tumble in the wind to spread seed

Photo of diffuse knapweed with white and pink flowers

Control

Mowing plants in bud to flower stage can reduce seed production; repeated hand removal can be effective; burning is NOT effective
Several insect biological control agents are available
Apply 2,4-D or dicamba in the rosette stage; apply aminocyclopyrachlor, aminopyralid, chlorsulfuron, clopyralid, imazapyr or picloram pre-emergence to rosette and 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 – Diffuse knapweed, Extension, University of Nevada, Reno, Field Guide

Extension Associated Contacts

Loretta Singletary

Also of Interest:


Water Sustainability and Climate in the Truckee-Carson River System, Western United States: 10 Key Takeaways from the Water for the Seasons Collaborative Research Program. This Special Publication briefly introduces the Truckee-Carson River System case study area, describes the Water for the Seasons research program, and presents 10 key takeaways from this five-year collaboration between local water managers and researchers. Sterle, K., Singletary, L., Lee, G.-E., Rollins, K., Pohll, G., McCarthy, M., Rajagopal, S., Albano, C., Boyer, W., Huntington, J., Dettinger, M., Niswonger, R., Morway, R., Kitlasten, W., Gardner, M., Coors, S., and Jose, L. 2020, Extension I University of Nevada, Reno, SP-20-02.
Climate Scenarios for the Truckee-Carson River System. Water for the Seasons partners scientists with community stakeholders in the Truckee-Carson River System to explore new strategies and solutions for dealing with extreme climate events such as droughts and floods. Dettinger, M.D., Sterle, K., Simpson, K., Singletary, L., Fitzgerald, K., and McCarthy, M. 2017, Extension I University of Nevada, Reno, SP-17-05.
Sustaining Water and Climate Resiliency in the Truckee-Carson River system Water for the Seasons partners scientists with community stakeholders in the Truckee-Carson River System to explore new strategies and solutions for dealing with extreme climate events, such as droughts and floods. McCarthy, M., Singletary, L., Sterle, K., Simpson K., Fitzgerald, K., Pohll, G., Rajagopal S., Huntington, J., Dettinger M., Niswonger, R., and Kauneckis, D. 2016, Extension \| University of Nevada, Reno, Fact Sheet FS-16-01
Managed Aquifer Recharge in Snow-Fed River Basins: What, Why and How? Water for the Seasons is a collaborative modeling research program that partners researchers with water managers representing the diverse water-use communities in the Truckee-Carson River System in California and Nevada. Sterle, K., Kitlasten, W., Morway, E., Niswonger, R., and Singletary, L. 2019, Extension I University of Nevada, Reno, FS-19-10

Associated Programs

Water for the Seasons

Water for the Seasons (WftS) is a program that partners scientists with community water managers and water right holders in the Truckee-Carson River System (TCRS), to explore new strategies and solutions for dealing with extreme climate events such as droughts and floods.

Nevada Noxious Weed Field Guide – Diffuse knapweed