Observed: September 9, 2011 @ 2:00 PM
Posted on: September 10, 2011 @ 5:21 AM (diff: 1 days)
The Bull thistle iis a biennial, reproducing only by seed. It is distinguished from all other thistles by the covering of short, sharp prickles on the upper, dark green surface of the leaf blade, these prickles (apart from the obvious spines along the margins and tips of the lobes) make the surface very harsh to the touch. Its purple flower heads are larger than Canada thistle.