Other common names
Common thistle, spear thistle
Bull thistle grows as a rosette (ground‐hugging form) in the first year, and then sends up stems and flowers in the second year, growing to 6 feet tall.
Pink to purple, vase‐shaped and in branched clusters at the ends of the stems. Bracts (modified leaves located under the flower petals) are spiny. Blooms from summer to fall.
Lobed, hairy and rough on the upper side; soft on the underside, with a raised center vein. Leaves are rough when rubbed towards the base. Lobe tips have long, stiff spines. The lobe at the end of the leaf is elongated.
Hairy, spiny‐winged and branched.
Forms many stiff, brown burrs. This is the point at which most people notice the plant.
Eurasia; naturalized to much of the United States.
Where it grows
Rangeland, roadsides, edges of fields, burned areas and other disturbed or mismanaged sites.
Biennial (flowers and dies in the second year)
Reproduces by seed
Bull thistle is easiest to control in the rosette stage. Prevent seed production to avoid spread by blowing seeds. However, simply cutting off the blooms does not provide sufficient control, as the plant will produce more flowers.