Cirsium vulgare
Copyright, Peter Sforza
Bull Thistle is a prickly
wildflower which most people consider an annoying
weed.
Its stems, branches, and leaves are covered with spikes and
you should be careful when touching it. Bull Thistles have pretty
purple to pink flowers, one to two inches wide. Leaves are
three to six inches long. Bull Thistles can reach six feet
tall. This plant, which is in
the Sunflower family, can grow in fields, gardens, and
roadsides. Bull Thistle is an introduced
plant, but is now common. Bull Thistle blooms from
July to September. After the flower has
finished blooming, the fruits produce "thistledown," small
seeds with fluffy stuff on them. This type of seed is called
an "achene." Achenes are transported
by wind to new places so new Bull Thistles can
grow. Copyright, Peter
Sforza Robert W.
Freckmann, Wisconsin State Herbarium The Bull Thistle is a
biennial
plant, which means it lives for two years and then dies. The
first year it grows a rosette,
a cluster of leaves near the ground. The second year it
grows flowers and fruits, spreading seeds before it dies.
The pictures to the left show a rosette the first year (top
picture), and a dead plant in the winter (bottom
picture). Bull Thistles are a good
food source for many animals. Eastern Cottontails and
White-tailed Deer eat the leaves and stems. Flower
nectar
is consumed by hummingbirds, bees, and butterflies. Seeds
are popular with many birds, such as American Goldfinches
and Juncos, as well as mice and other small
mammals. Hummingbirds and insects
help pollinate
Bull Thistles by accidentally gathering pollen from one
plant, and delivering it to the next one they
visit.
