Abstract:
Bull thistle is native to Europe, western Asia,
and North Africa. It probably was introduced in
eastern North America during colonial times, as
a contaminant in seed or ship ballast. It is now the most
widespread of the thistles in the United States (Figure 3,
next page) and is commonly found in disturbed areas
such as roadsides and burned or newly logged forests.
It invades a variety of habitats where it displaces native
plants by out competing them for water, nutrients,
and space. It does not grow well in shade. Bull thistle
reproduces only by seed. Individual plants set seed
before dying, and a single large plant can produce tens of
thousands of seeds.
