Canada thistle is one of the big nasty perennial weeds
that infest millions of acres (hectares too). They invade pastures and row crop and just
about any land they can. They seem to thrive in drier habitats, although they are very
open-minded about invading your farm. Their success is in no small part due to their very
aggressive rootstock-root-bud system, as seen in the picture on the left.
Once buds on the rootstock germinate they form seedlings
(left).
Leaves are spiny and hurt when you try to pull them with
bare hands. The small plant (left) didn't seem to be hurt too much by the severe summer
hail storm that took place just before I took this picture (left).Leaves and stems:
