Thistle, Bull

Cirsium vulgare is another noxious weed in Minnesota to eradicate and control as it is invasive and easily spreads. Like plumeless thistle, bull thistle is overall very spiny — another way to differentiate between the exotics and our native thistles which have fewer spines or are softly spined. Unlike plumeless thistle, bull thistles are distinctive with their rather large flower heads and rather bulbous beneath, 1.5 to 2 inches across for the flowers, bracts narrow and spreading with short spines on their tips. In contrast, plumeless thistle heads are 1″ or less across.

Bull thistle flowers grow solitary on the ends of branches, or with a few clustered at the ends of branching stems. Plant height can reach 6 feet.