Canada thistle Vol. The grooved, slender stems branch only at the top and are slightly hairy when young, becoming covered with hair as the plant grows. The oblong, tapering, sessile leaves are deeply divided, with prickly margins.
Leaves are green on both sides with a smooth or slightly downy lower surface.
Canada thistle should be accurately identified before attempting any control measures. Distribution Canada thistle, which is naturalized from Europe, occurs throughout the northern U.S. east of the Rocky Mountains. It is common in the northern half of Illinois and rare in the southern half. This species is very rare in southern Indiana and is not a serious problem in Missouri natural areas. It can invade sedge meadows and wet prairies from adjacent disturbed sites.