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. It is scattered throughout the northern two-thirds of Missouri. Missouri distribution is poorly documented due to a lack of collecting of weedy thistles by botanists. It can invade sedge meadows and wet prairies from adjacent disturbed sites. This thistle does not do well in undisturbed prairies, good to excellent pastures, or in woodland.