A variety of thistles are found in turf. Like most, bull thistle is a biennial. It grows over the summer months. The leaves are alternate; blades are simple and form in a rosette. The leaves are unlobed to pinnately lobed. The blade tip is pointed and the margins are toothed with spines. The root is a fleshy taproot the first year and a fibrous root system forms the second year. The second year of growth, thistle stems elongate. The elongated stems have alternating leaves. Flowers are present from June through October on the elongated stems. The disk flowers are dark pink to purple with spined bracts. Bull thistle spreads by seeds. Thistles are found throughout the United States and Canada.
Individual bull thistle plants can be physically removed by cutting below the crown in early spring. Bull thistle should be removed prior to bolting and flowering to prevent seed development and distribution. Follow good turf management practices to create a dense competitive stand of turfgrass.
Thistles that are actively growing and in the rosette to flower stage of growth can be controlled with a post-emergence herbicide application.