Nodding Thistle
Carduus nutans)

Nodding thistle, while lovely, is a menace.  Introduced to North America from Europe early in the 20th century, it is spreading rapidly throughout the United States.  The basal rosette is formed during the plant's first year and stays green all winter long, killing all plants it covers.  Up to 10,000 seeds are produced by a single plant and spread by silky parachutes.  The plant is found in waste places, roadsides, neglected pastures and railroad rights of way.

The scientific name actually means nodding thistle.  Another name for this plant is Musk thistle.