Canada Thistle
Scientific Name: Cirsium arvense (L.) Scop.
Other Names: Creeping thistle, perennial thistle, and green thistle.
Life Cycle: Perennial
General Description: A rhizomatous perennial with lobed, spiny leaves and pink flowers.
Seedlings: Cotyledons are oval to round and pale green in color. Young leaves
are thick, lanceolate, and covered in short hairs. Margins are wavy
lobed with spines. Shoots emerging from rhizomes lack in cotyledons, but
initally form rosettes.
True Leaves and Stem: Leaves are alternate, sessile, oblong to lanceolate,
irregularly lobed with spiny margins. Upper leaf surface is smooth. The
base of each leaf surrounds the stem. Stems are grooved and smooth to
slightly hairy.
Roots: Rhizomes extending up to 1m deep.
Flower and Fruit: Flowers are pinkish purple and arranged in clusters. Plants are dioecious (separate male and female plants).