Like most composite flowers of the aster family, the radially symmetrical bull thistle bloom is comprised of numerous, long, rayless, pink or white flowers. The flower cluster, measuring approximately 4-5 cm. in width, rests atop a large, round structure comprised of spiny, green and black, yellow-tipped bracts.
The seed-like fruit, measuring 5 mm. in length, is elongated and tipped with numerous, wind-catching, bristles.
The leaves of the bull thistle are long, measuring 7.5-15 cm. in length, and are coarsely lobed. They are robust and covered in sharp spines
Bull thistle grows best along roadsides, in pastures, and around waste areas.
Bull thistle is a very dangerous plant. The sharp spines that cover virtually every surface of the stem, leaves and flower head can easily puncture and irritate skin.
The bristles found on the fruit of the bull thistle are appropriately named "thistledown". These bristles are sensitive to wind and allow for wide dispersal of the bull thistle fruit.