Canada Thistle(Cirsium arvense)

Stem: Hollow and may grow to a height of 1 metre (1 to 4 feet).

Leaves: Irregular shaped spiny lobes.

Flowers: Are usually purple but may appear white and are urn-shaped.

Problem: Despite its name, this plant is not native to Canada. Canada thistle is a perennial that spreads both by seed and by an aggressive underground root system. This weed greatly reduces species diversity on rangeland and on natural areas and acts as an alternate host for crop diseases.