Mature Plant

Description: Bull thistle grows most often as a biennial, reproducing only by seed. During the first year of growth, a large basal rosette with a large tap root is formed. During the second year of growth, an erect flowering stem grows to a height of 2 to 4 feet. The stem is large, branched, and covered with dense hair. Leaf bases extend down the stem to give the stem a winged appearance. The leaves are alternate, dark green, coarsely lobed, with 3 to 4 points per lobe, each ending in a long sharp spine. The upper surface of the leaf is covered with short, stiff hairs and spines, and the underside of the leaf is covered with dense, woolly, gray hair. The flower heads are compact, 1 to 2 inches in diameter and each flower head is surrounded by spine-tipped bracts. The flowers are reddish-purple. Flowering occurs from late June through August and the seed matures in July through September. The seeds are 1/8 inch long, oblong, flattened, and curved and are light brown with dark brown stripes.

Seedling

Distribution: Bull thistle is primarily found in pastures, waste areas, and along roadsides. Bull thistle is found throughout Minnesota and can be found on a variety of soil types.