Which of the following is an example of an annual weed?

An annual weed is characterized by its life cycle, which typically lasts one growing season. These plants germinate, grow, flower, produce seeds, and die within the span of a year. Pigweed is a prime example of an annual weed because it completes its life cycle within a single year. This allows it to reproduce quickly, often leading to significant populations in disturbed areas, including agricultural fields and landscapes.

In contrast, the other plants listed have different life cycle characteristics. Common mullen is a biennial plant, meaning it takes two years to complete its life cycle, while field bindweed and musk thistle are both perennial weeds, which live for multiple years and can regrow from roots or seeds over several seasons. Understanding these distinctions helps in effectively managing and controlling these different types of weeds.