Pest Management Weed biology - Weed Management Weeds are grouped into three categories based on their life cycles.
Annuals complete their life cycle within one year and reproduce from seed.
Winter annuals germinate in the fall and complete their reproductive cycle in the spring or early summer. Summer annuals germinate in the spring and set seed in late summer or fall. Summer annuals thrive when summer annual crops like corn or soybeans are grown. They compete directly with the crop for resources. Biennials live during two growing seasons.