BACKGROUND: Originally found in Eurasia, spotted knapweed infests rangeland, pastures, roadsides, or any disturbed soils. Knapweeds release chemical substances into the soil that inhibit the growth of competing vegetation.
DESCRIPTION: Spotted knapweed is a short-lived, herbaceous perennial that is 1 to 3 feet tall. The rosette leaves are deeply lobed and may be 6 inches in length. The stems are moderately leaved. Flowers are typically pink with black-tipped flower bracts. Bloom is in early summer.
CONTROL: Several biocontrol agents are available and offer fair to good control. Select herbicides can offer good to excellent control when applied between rosette and pre-bud stages.