Canada Thistle

080717_scots_thistle.jpgScientific Name: Cirsium arvense
Common Name(s): Canada thistle, Canadian thistle, Californian thistle, corn thistle, field thistle, creeping thistle, perennial thistle

Origin: Canada thistle was first introduced to the United States during the 1700s. It quickly became known as a contaminated crop seed. Its able to reproduce through seed and root regeneration. its one of the first plants that have been imported to North America by settlers. Its native to Eurasia.

Identification: The Canadian thistle can be easily identified by their small clustered purple flower heads. The plant can reach up to 5 feet tall. The roots are white, and spread out to the sides just beneath the soil.

Characteristics: Canadian thistle pllants can be produced from either the root bud or their seeds. The Canadian Thistle is able to produce up to 1,500 seeds during a successful polination. Having more then 5,000 per plant from production makes it highly unwanted and tough to get rid of. The seeds can be carried for a long distance because of the feathery hairs called a pappus. Some of the seeds survive up to 21 years when burried. When burried in warm, moist soil and have full light, they become viable for 3-6 years. A typical seed is no longer then 3mm.
They become stressed under competition but once they're established they quickly become a problem because of their extensive root system.CanadaThistleSmall.jpg

Habitat: Canada Thistle plants are most likely found along roadsides, old feilds, waste places and fence rows. it can also be found in moist areas like ditches and along river or stream banks. This weed will not hold well in woodlands or dry praries.

Control:The plant spreads quickly, while invading crop lands costing millions, and threatening the ecosystem and parklands, Canada thistle can be tricky to control. A few inexpensive ways to help control this plant are;
Burning: Controlled burning is best in late growing season. During early spring can cause encouraged thistle growth.
Hand-cutting: Its best to cut off the seed head and continue cutting as low as possible. If you perfer to dig, make sure you go deep enough to extract the crown.
Mowing: Be sure to mow the plants in spring or late summer when they are they starting to flower. Mow as close to the ground as possible to ensure the whole plant is gone. Continuous mowing will be needed throughout the years to control these perennials.
Seeds may lay dormant for up to 20 years, repeated treatment may be needed.
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References: www.weedsbc.ca/resources.html
http://www.agriculture.gov.sk.ca/Canada_Thistle_Control