An annual weed is just one type among three: annual, perennial, and biennial. Annual weeds: These weeds live for one year or one growing season (can overlap calendar years). --Summer annuals: These weeds sprout in the spring, reach maturity during the summer months, and set seeds in the fall. They die during the fall or after a hard frost. --Winter annuals: These weeds sprout in late summer or early fall, overwinter, and put forth flowers in the spring. By early summer, they die. Biennial weeds: These weeds put forth roots, stems, and leaves the first year and go dormant that winter. During the second year of life, they flower, set seed, and die. Perennial weeds: Perennial weeds live for three or more years. Some perennials produce seeds but most reproduce vegetatively through tubers, stolons, rhizomes, or bulbs. These weeds are among the most difficult to eradicate.