The leaf bases extend down to the stem, and the leaves become progressively smaller up the stem. Solitary flower heads are produced at the end of branches. Individual flowers are 1 to 2 inches wide and are pink to violet or purple in color. Spiny bracts occur below the flower heads and these are often tinted purple in color. An achene that is tan to brown in color and approximately 4 mm long.
Achenes are oblong in outline and have a white pappus that resembles white hairs.
Erect, spiny biennial with deeply lobed leaves and relatively large flowers that are pink to violet or purple in color. Additionally, the flower heads and bracts of bull thistle gradually taper to a point when compared to those of musk thistle.