Annual weeds are plants that reproduce by seed and germinate each year. Some common annual weeds include foxtail, velvetleaf, and cocklebur. Winter annuals germinate in the fall and complete their reproductive cycle in the spring or early summer. Summer annuals germinate in the spring and seed out in late summer or fall. Summer annuals flourish when summer annual crops such as corn or soybeans are grown, competing directly with the crop for resources.
Biennial weeds live through two growing seasons, although they also reproduce via seed.
The first year is devoted to vegetative growth, and the second year has both vegetative and reproductive growth. Because of the 2-year cycle of growth, these weeds are found in areas of low soil disturbance such as pastures, waterways, and fence rows. Perennial weeds grow for more than two years and are quite versatile, able to thrive in both areas of reduced soil disturbance or fields of row crops. Plant seeds are dispersed in a variety of ways. Leafy spurge seed pods build up pressure and explode, shooting seeds up to 15 feet away.