Scientific NameCirsium arvense
Other Common Names:
Synonyms (former Scientific Names):
Cirsium arvense var. integrifolium
Cirsium arvense var. horridum
Cirsium arvense var. argenteum
Cirsium arvense var. vestitum
Canada Thistle produces flowers from about June until August. Generally, new shoots begin to form in January. The species spreads by creeping roots which in turn causes Canada thistle to often form dense patches.
Leaves are generally oblong with edges that are lobed and spiny. Leaves are dark green and smooth on top portion and light green and often hairy on the lower portion. Leaves are attached to stems by way of a clasping base.
The plant reproduces by seeds and dense patches of shoots emerge from creeping roots.
Flower Seed Head
Small lavender flower heads consist of as many as 100 lavender tubular flowers. Flower heads are flask-shaped, 1/4 to 3/4 inch wide. The flower heads are produced singly or in groups of 2 to 5 at the ends of stems and axillary branches.
Mature seeds are brown, 3/16 inch long. A plume of tannish silky hairs is attached to one end.
The Canada thistle plant grows in cultivated fields, pastures, rangelands, roadsides, waste places, and other open areas.
upright and nonwoody
Thorns or Spines
Approximate Flower Diameter
Dominant Flower Color
Stem Cross Section
round or oval