Stem

To 5 ft. tall; forms basil rosette, then rapid growth forms flower stems; lower parts of flowering stems are winged

Leaves

Fuzzy leaves with deep, rounded lobes; leaves decrease in size higher on the plant

Flower

White to pink to purple petals, 0.5 in. tall and 0.5 in. wide with fuzzy hairs at their base; flowers often appear to have no petals; bracts at the base of the flower have light brown, pointed spines; seeds are tiny, barrel-shaped and have a crown of fine hairs that aid in wind dispersal

Root

Stout, deep taproot and many fine, water-absorbing, surface roots

Other

Grows best on disturbed ground and seasonally flooded sites; no known occurrences in Nevada
Winter annual; each plant can produce several thousand seeds; seed remains viable in soil for several years
Can outcompete native vegetation by rapid growth which shades out other plants

Control

Mechanical removal by pulling, digging or hoeing is effective; if plant is flowering, bag up plant and dispose of properly
Apply aminocyclopyrachlor+chlorsulfuron, aminopyralid or clopyralid preemergence or post emergence in the seedling to rosette stage; apply 2,4-D or dicamba post emergence during rosette to early bolting stage

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

Learn more about the author(s)

Heidi Kratsch

Also of Interest:

Nevada Noxious Weed Field Guide – Mediterranean desert knapweed