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

Stem

Up to 2 ft. tall, highly branched and rough-textured; multiple stems can arise from woody crown; NO wings on upper stems

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)

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

Root

Deep, stout taproot

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

Learn more about the author(s)

Heidi Kratsch

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Winter Lettuce Trial The concept of the project was to investigate if lettuce could be produced in the field and harvested throughout the winter season. Prior to the project trials, DFI has grown leaf lettuce in hoop houses during the winter season with relative success. Schembre, C. 2019, Desert Farming Initiative (DFI), University of Nevada, Reno
A Northern Nevada Homeowner’s Guide to Identifying and Managing Prickly Lettuce Guide to identifying and managing prickly lettuce, a bushy, much-branched drought-tolerant plant that grows to five plus feet tall. Donaldson, S., Hanson Mazet, W. 2010, Extension \| University of Nevada, Reno FS-10-28
Head Lettuce and Produce Safety Produce safety needs to be taken into consideration during lettuce production. This fact sheet highlights key guidance, practices, and resources for lettuce growers. Moe, J. 2020, Desert Farming Initiative (DFI), University of Nevada-Reno

Nevada Noxious Weed Field Guide – Squarrose knapweed