Canada Thistle (Circium arvense)
Thistle Species-Group
Composite (Compositae) Family

221t.JPG (10547 bytes) 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.

774t.JPG (12571 bytes) Once buds on the rootstock germinate they form seedlings (left).

299t.JPG (11652 bytes) 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:

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Flowers and seedheads. This bee (left) seems to like pollinating this flower even though its efforts result in seeds, the second way Canada thistle reproduces.

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©jdekker-1998

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