(Cirsium arvense L.)
Life Span: Perennial
Origin: Eurasia and North Africa
Reproduction: Rhizomes (roots) and Seeds
This plant is one of the reasons why there is a noxious weed law in place today. Back in the early 1900’s, the Noxious Weed Act was known as the Canada Thistle Law, which gave a person the right to eradicate Canada Thistle on anyone’s property, including their own, and not be held for trespassing.
It was introduced from southeastern Eurasia into Canada as a contaminant in crop seed as early as the 18th century. It is found throughout the North Central and Northwestern parts of the U.S., as well as in most of Canada. By the way, its not “Canadian” but Canada Thistle.
The reason this plant is considered noxious is:
1. Its a deep rooted perennial and forms colonies.
2. Spreads by root sections, as well as by seeds.
3. Loves pastures and hay meadows, can be found in No-till crops.
4. Very costly to control.
5. Negative impact on Agriculture Economics.
Canada Thistle grows from a rosette in the early part of the season to a plant about 3 to 4 feet tall. The white-pink-purple flowers are clumped together forming a small seed head. The Leaves have very short spines and are shallow lobed. Canada Thistle is different from all other Thistles by the fact that it needs a male and female plant in the vicinity to create seeds. It also spreads by rhizomes (creeping roots) just below the surface, causing it to be found in tight patches.
For a more detailed description of Canada Thistle, check out the Nebraska Weed Control Association Website.