Cirsium arvense



Scientific Name: Cirsium arvense
Common Names: Canadian Thistle, California Thistle, Creeping Thistle
Kingdom: Plantae
Subkingdom: Tracheobionta
Division: Magnoliophyta
Order: Asterales
Family: Asteraceae
Genus: Cirsium Mill. (thistle)

FamilyThe Asterceae family also called the Compositae is one of the largest plant families. The family is known primarily for its many garden ornamentals such as asters, dahlias, and marigolds. However, the family also includes such noxious weeds as the dandelion, the endive, and the thistle. Some of these weeds are economically important for the products derived from their seeds, leaves, and tubers. In this family, many of the plants have flower heads composed of small flowers called florets. In addition, these weeds contain a one-seeded fruit called an achene that has a hard outer covering. Finally, the first members of this family are believed to have evolved in Argentina some 50 million years ago.

  • Reproduces primarily vegetatively through creeping horizontal roots, and can quickly form dense stands.
  • Every part of the root system has the ability to form a new plant; Thus reproduction can occur without seed production
  • a female Canada thistle can produce up to 5,200 seeds in a season, but the average is around 1,500.
  • Seeds are distributed by wind and seeds that do not germinate may remain dormant for several years.

Distinguishable Traits---Physical Appearance

  • are spiny, alternate, oblong-shaped with a stalkless base or extending down along the stem



  • Flowerheads are purple and borne in clusters with one-seeded fruits



  • Two types of roots
  • Horizontal roots produce numerous shoots
  • vertical roots store water and nutrients

Canada_Thistle10 root.jpg

Human Uses
Nutritional Benefits?

  • The leaves of the Canada thistle are a source of fiber, vitamins, and minerals
  • The roots can also be de-spined and eaten raw or steam-cooked

Medicinal Benefits

  • North American Indians once used Canada thistle roots for mouth disease and infections through infusions and extracts
  • The weed was thought to produce healing properties in tonics and astringents
  • The leaves also posses anti-inflammatory properties when chewed
  • The juice of the roots can also be ingested to allieve intestinal issues caused by parasites in the stomach

Invasive Strategies
Why has the species been able to invade a specific environment?
  • High growth rate-- 3-6 feet per year; crowding out more desirable species and creating thistle monocultures
  • Once it has established itself, it spreads quickly replacing native plants and diminishing diversity.
  • Spreads in circular patches of up to 12' in one season
Damage done to the Environment?
  • Extensive root system allows the weed to out-compete and displace many native species, especially in prairies
  • Damages grazing grasses for livestock, crops and pastures

Control Methods:
What has been used to stop the invasion?

  • Different methods of mechanical or chemical processes can be utilized to control the spread of the Canadian thistle, yet there are no known biological methods that have been effective
  • Mechanical Methods
    • Prescribed burning, during spring time, can be effective by reducing thistle density and allowing native species to compete for resources
    • Mowing will temporarily reduce the amount, but will not kill the weed and may also harm native plants as well
    • Hand pulling is generally regarded as ineffective since small portions of broken taproot can easily regenerate
  • Chemical Methods
    • Foliar spraying of sytemic herbicide such as Roundup, Glypro or Transline is an effective control method
    • Fall and Spring are usually the best times to utilize chemical methods as to maximize the herbicide absorption into the deep taproot.



Where is it located in the world?

  • Canada Thistle thrives in the Northern Temperature Zone, best adapting to rich, heavy loam, clay loam, and sandy loam, with an optimal soil depth of 20 inches. The weed is found throughout the northern half of the United States and lower portions of Canada.
Where did the plant originate from?
  • The Canada thistle is believed to originate from Southeast Eurasia. It was initially introduced to Canada as a contaminant of crop seed in the late 18th century, but quickly spread throughout North America.
In what type of environment does it grow?
  • Canada thistle mostly finds habitat in disturbed areas, but also invades native plant communities, open meadows, and ponderosa pine savanna. The weed is adapted to a wide range of soil types as stated earlier and can tolerate saline soils and wet or dy soil.
  • The weed is commonly found along roadsides, fields, pastures, and meadows


"Wildcard"Case Study of Cost Benefit Analysis of Chemical Methods for Canada Thistle Prevention
Research Conducted in Sample Study at Colorado Farm
  • Usage of Chemical agents AllDown, Deadeye, and variants of AA
  • Experiments with different treatment plans through different week intervals
  • Best method turned out to be an aggressive strategy using one of the chemical agents at two week intervals early in the season
  • Takes more than 2 years of non-tillage treatment to eradicate established stands of Canada thistle
  • Mechanical treatment proved to be too tasking for how ineffective it proved
  • Notes on study conducted------

Undefined, Accessed April 21, 2013. Published on March 27, 2013