bull thistle
Family
AsteraceaeScientific Name
Cirsium vulgareOther Common Names:
common thistle
spear thistle
thistle
Synonyms (former Scientific Names):
Cirsium lanceolatum
Carduus vulgaris
Carduus lanceolatus
Habit
Bull thistle blooms from June to October. Bull thistle rosettes remain green and continue growing throughout the winter.
Leaves
The rosette leaves ranging between 3 to 7 inches long. The upper portion of the leaf is dark green and covered with sharp prickly hairs, while the lower portion of the leaf is a lighter green and is covered with soft hairs that have a wooly feel. The stem leaves are somewhat similar to rosette leaves just smaller in size. Leaves are attached to the stem and extend down it offering a winged looked. Leaves are indented around the edge with groups of 2 or 3 spine-tipped lobes interspersed with non-lobed portions.
Identifying Characteristics
Reproduction is performed only through the seeds. Bull thistle plants can produce approximately 7000 seeds.
Flower Seed Head
The flowers are located at the end of stems covered in spiny hairs. The outer rim of the flower is green and spiny itself, and contains many disk shaped flowers that are reddish-purple.
Seed Fruit
The seeds are straw colored with a black streak approximately 1/6 inch long. One end of the seed contains many brown hairs.
Where Found
The bull thistle is now established on every continent except the frozen tundra of Antarctica. It grows as a weed in pastures, roadsides, and fields that have been abandoned. It prefers disturbed areas with rich and moist soils.
Growth Habit
upright and nonwoody
Thorns or Spines
present
Approximate Flower Diameter
Varies:
nickle,
quarter,
half dollar,
larger
Dominant Flower Color
Varies:
purple,
red
Flower Symmetry
radial symmetery
Leaf Hairs
has hairs
Leaf Shape
oval
Leaf Arrangement
Varies:
alternate,
opposite,
rosette
Leaf Margin
Varies:
entire,
lobed,
serrated
Leaf Structure
simple
Leaf Stalk
none
Stem Hairs
has hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
taproot
Life Cycle
biennial
Ochrea
not present
Plant Type
Herb