This, mostly biennial plant, is one of the most common and widespread
of all thistles in North America. The leaves of this plant are lance-shaped,
and prickly. The undersides are very hairy. The lobes of the leaves have
long stout spines extending from them. The flower heads usually 1.5 to
2 inches in diameter and similarly long. These clusters, which are generaly
smaller, do not usually droop over like they do in musk thistle.
Two other invasive thistles, which can be confused with bull thistle
that are very common and problematic are musk
thistle and scotch thistle.
Bull thistle is native to Eastern Asia, Europe and Northern Africa and
was introduced to North America in colonial times. It is believed to have
spread to the western US by the late 1800's and today is found in every
state, including Hawaii.