How Do I eradicate Canadian Thistle?
Canadian thistle is a creeping perennial which reproduces from vegetative buds in its root system and from seed. It is difficult to control because its extensive root system allows it to recover from control attempts. However it sounds like you are already doing the right thing by cutting it down, which should, eventually exhaust the root system. However, apparently you should not cut it to the ground, as that will encourage the spread of the root system. Rather leave stock about 8 inches long and keep cutting it off at the that length. And never let it go to seed!