Annuals complete their life cycles in one season by flowering, maturing seed and dying.
Their high seed production serves as a ready source for infestation when conditions are favorable. Summer annuals germinate from late March through July, depending on the location. They flower in the summer and either die in the fall or are killed by frost. Winter annuals germinate in the fall and early winter and may continue to grow into early summer in cool seasons. Perennials live more than two years and may produce seed each season.