Which plant is nicknamed the tumbleweed?

The plant referred to as the tumbleweed is the Russian thistle. This nickname is derived from its unique characteristic of detaching from its root system when mature and rolling across the ground with the wind. This behavior allows the plant to disperse its seeds over a wide area, contributing to its spread in regions, particularly in North America.

Russian thistle is a member of the chenopod family and thrives in arid environments, playing a significant role in those ecosystems. Its distinctive shape and method of seed dispersal have made it a well-known and often iconic representation of arid landscapes, especially in Western United States.

The other options do not exhibit the same tumbleweed characteristics. For example, green foxtail and Canadian thistle do not have the same rolling or free-moving nature when they mature. Common thistle, while a well-known plant, also does not share the tumbleweed's method of seed dispersal. Each of these plants has different characteristics and life cycles that do not align with the defining features of a tumbleweed, which highlights why Russian thistle is the correct choice.