this biennial weed is common in pastures and open fields. A tough perennial with thistle-like purple flowers. It's invasive ...

After all, just because the frost killed all purple flower invasive weeds doesn't mean it got to their seeds or root fragments, too. Given that, it's pertinent to learn to spot the purple bloomers ...

Flowers are unisexual, on separate plants; flowers purple (occasionally white) in heads 1/2 to 3/4 inch in diameter ... By asexual reproduction, it is possible that a colony of male plants would ...