Musk Thistle (Nodding Thistle)
Musk thistle is a large, spiny biennial with rose-purple flower heads up to 2½ inches wide. The stems are commonly winged with spiny leaf tissue. The plant forms basal rosettes during its first year, which have deeply lobed leaves that are up to 10 inches long and 4 inches wide, and have a prominent, nearly white center vein. During the second year, an upright flowering stalk grows that has smaller, very spiny leaves. The flower heads are mostly solitary and nod at the branch tips. At the base of each flower head are numerous, spine-tipped bracts, 1/8 to 3/8 inch wide, that curve away from the heads. Blooms June through October. A single plant can produce 11,000 seeds, spread by silky parachutes.
Similar species: Our native thistles have strongly whitened undersides to the leaves, whereas this thistle (and other exotic thistles) has both sides of the leaves the same color.