(Centaurea solstitialis L.)
Sunflower family - Asteraceae
Photo from Weeds of the West, revised edition.
Photos from Montana Weed Control Association
Toxic: To Horses
Growth Habit: Annual, erect, rigid brancing stems.
Leaves: Basal leaves deeply lobed, upper leaves not lobed, small, sharply pointed.
Stem: Rigid, covered with a cottony fiber, to 30" tall, winged structures.
Flower: Yellow, terminal, flower bracts are tipped with straw-colored, 3/4 inch thorn.
Seeds: Smooth, light-colored, often darker mottled, 1/8 inch long, notched just above base.
Habitat: Rangelands, pastures, vineyards, abandoned croplands, alfalfa and small grain fields and roadsides.
Biological Controls: Seed head fly (Terellia uncinata).
Herbicides: None used in Yellowstone County at this time.
Produced by Wyoming Weed & Pest Council in cooperation with Sandoz Crop Protection Corp.