Which of the following is NOT an example of a summer annual?

Summer annuals are those plants that complete their life cycle in one growing season, typically germinating in the spring, growing through the summer, and then dying off with the onset of winter. This includes weeds like pigweed, crabgrass, and Russian thistle, which are all adapted to thrive in the warmer months.

Henbit, however, is classified as a winter annual. This means it germinates in the fall, overwinters as a seedling or young plant, and then resumes growth in the spring, flowering and producing seeds before dying off as the weather becomes too hot in the summer. This distinct life cycle differentiates henbit from the other choices, making it the correct answer as the option not representative of a summer annual. Understanding the growth patterns and life cycles of these plants is vital for effective weed management strategies in agricultural settings.