Which type of thistle is perennial and has a greater root system?

• A. Musk thistle
• B. Canada thistle
• C. Bull thistle
• D. Dandelion

Answer: (B)

The main idea here is understanding how a weed’s life cycle and its root system affect how persistent it is. Canada thistle is a creeping perennial, which means it lives for many years and spreads underground through a network of rhizomes. That rhizome system can extend far and send up new shoots, so a single plant can become a large, long-lasting patch. This combination of being perennial and having an extensive underground root network makes Canada thistle noticeably more persistent than other thistles that rely on a taproot or don’t spread as extensively. Musk thistle and bull thistle are typically not as deeply or broadly rooted, and dandelion, while perennial, isn’t a thistle at all. So, Canada thistle best fits the description of perennial with the greater root system.