What characterizes a summer annual?

A summer annual is characterized by its life cycle that begins with germination in the spring. These plants grow and develop throughout the warmer months, completing their life cycle by producing seeds and dying off by the fall. This adaptation allows them to take advantage of the longer days and warmer temperatures of summer for their growth and reproduction.

In contrast, other options highlight different growth patterns not typical of summer annuals. Some plants may grow year-round, which distinguishes them as perennials, while others may only germinate and grow in winter, highlighting that they are winter annuals. Additionally, the option that mentions activity during the fall and winter months relates to plants that do not follow the summer annual lifecycle, as those growing in that period would be more suited to other seasonal classifications. Thus, the clear definition of a summer annual relates directly to its germination in spring and harvest in the fall, making it the correct answer.