In the scientific name of Canada thistle, "arvense" is Latin for "of the field" or "arable field," which is where Canada thistle is commonly found. The relevance of the word "Cirsium" is more obscure. It is from Greek meaning, "a swollen vein." This term probably refers to the fact that thistles, not necessarily this one, were used in medical treatments.
Canada thistle, despite the name, was probably introduced into North
America in the 18th century as a seed contaminant from
Therefore, flower pollination is dependent on wind and insects. Seeds are only about 1/8 inch (0.3 cm) long, dark brown and are attached to a tannish down called pappus. This down allows the seeds to be easily scattered by the wind. The root system of the Canada thistle can reach 10 to 15 feet (3 to 4.6 m) deep. Canada thistle sends out horizontal roots, which classifies it as a "creeping" perennial weed. Horizontal roots and the capability to quickly produce seeds, give the plant the ability to spread quickly. Each Canada thistle produces up to 680 seeds, which can mature in 7 to 10 days after the first flower. One plant, left undisturbed, can multiply to cover a one-half acre patch within 3 years.
Early detection and control of Canada thistle is essential, especially during times of abundant moisture. One method of control is by the cultivation of a crop such as alfalfa. The repeated cuttings help control the weed. Another method is the introduction of a biological control agent. With this method, the natural control agent of Canada thistle, in many cases an insect, is introduced. In South Dakota the use of biological control is just in the experimental stage.
The South Dakota Weed and Pest Control Commission has the legal responsibility for developing and implementing a statewide control program for all noxious weeds. South Dakota law requires that all land owners control noxious weeds on their land. If land owners do not comply with noxious weed control requirements, fines, tax levies, and liens against their land could result.
Biennial - a plant that requires two years to complete growth.
Noxious weed - designation of the State Weed Control Board. They are weeds that have become difficult to control once they are established.
Perennial - a plant that lives more than two years.
Agricultural Extension Service, South Dakota State University South
Dakota Weeds, 1974. South Dakota Weed Control
Cooperative Extension Service, South Dakota State University, U.S. Department of Agriculture, Canada Thistle Bulletin FS 896 CT. SDSU Cooperative Extension Service.
Klingman Glenn C., Weed Science 1982 John Wiley & Sons Inc. NY.
U.S. Department of Agriculture. Noxious Weeds of South Dakota Extension Special Series 34. SDSU Cooperative Extension
Zimdalhl, Robert L., 1989. Weeds and Words: the Etymology of the Scientific names of Weeds and Crops. Iowa State University Ames.
Noxious Weeds of South Dakota , Extension Special Series 34,
1993. Cooperative Extension Service, SDSU, Brookings, SD 57007.
South Dakota/Nebraska Weed Identification Guide, 1994. Black Hills RC&D Office, 515 9th Street, Rapid City, SD 57701-2663.
John Neff, USDA Americorp member, Fort Pierre, SD. 57532. 1996.
Leon Wrage, Extension Weed Specialist, SDSU, Brookings, SD.
Publication of the Canada Thistle fact sheet was funded by the
Northern State University CUEST Center for Environmental
Education, Aberdeen, SD.