On July 8, 2005 Roger Batt, Idaho Weed Awareness Campaign Coordinator, and Bryan Dallolio, Ada County Noxious Weed Control, found this large patch of the Canada Thistle right in the middle of the desirable grassy native plant called Sorghum. Roger notes that Canada Thistle is very prevalent in the state of Idaho and is virtually in every county. He asks Bryan to explain some details about this weed. Bryan responds by stating that Canada Thistle is a long lived perennial. It has a creeping root stalk and is very invasive. That is what makes it a noxious weed. Bryan notes also that it is known to spread somewhat by seed, but everyone agrees that this plant reproduces primarily by rhizomes.
Note that there are several video "hot spots" available which provide a lot more detailed information.
Panorama and video taken 7/8/05