Vascular Plants of Wisconsin
vulgare (Savi) Ten.
type: forb; biennial
Cirsium vulgare is a large, spiny plant of sunny
disturbed sites. The leaf blade continues down the stem
from the point of attachment resulting in "winged"
stems. The margins and lobe tips of leaves and stem wings,
and bracts of the flower heads all bear sharp, stiff spines.
What appears to be a large purple flower, is really a "head"
of flowers. When mature, the achenes each bear a cluster
of feathery bristles known as a "pappus" that
assist in dispersal by the wind.
Cirsium vulgare is an alien weedy species that has
become established throughout the continental United States.
It is found throughout Wisconsin in sunny sites, and is
especially prominent in farming areas, but can be expected
on productive soils just about anywhere. The plants are
biennial, meaning that they produce a basal rosette of leaves
in the first growing season and then send up a flowering
stalk in the second year. After they flower and produce
mature fruit in the second year they die. There are 10 species
of thistles (in the genus Cirsium) reported in Wisconsin.
Five of the species are aliens and they are the most common.
Two of the native species are threatened in Wisconsin and
one of those, dune thistle (Cirsium pitcheri) is
also federally threatened.