Canada thistle a challenge to control

Canada thistle was probably introduced to America around 1750, and the state of Vermont enacted noxious weed legislation against it in 1795. It was proclaimed a noxious weed in Nebraska in 1873. Obviously it has a long and tenacious history in the United States.

Canada thistle is a perennial that reproduces from both seed and extensive horizontal roots. These roots can grow as much as 9-18 feet laterally and 6-9 feet deep in a single growing season! If roots are cut by cultivation or tillage, segments as small as 1 inch in length can survive and establish a new plant.

Both male and female plants are needed for cross pollination and seed production to occur. Female plants are the most prolific, producing up to 5,000 seeds per plant! These seeds can remain viable in the soil for up to 20 years. These characteristics make the plant very challenging to control.

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