Since winter annuals do not compete with corn, they are not usually considered serious weeds. Conventional soil preparation for corn planting controls them adequately. Fall panicum may be an exception. To manage annuals it helps to think that their main purpose in life is to reproduce. Common annual weeds include lambsquarters, pigweed, ragweed, and crabgrass.
Biennials take two years to complete their life cycle.
Therefore they put their energy into producing root reserves. Often the aboveground portion of a biennial plant is a short rosette of leaves. This has important ramifications for control. Herbicides which work after being transported to the roots are effective the first year while the plant is translocating food to the roots. They do not work well the second year when the plant is pulling reserves out of the root to produce stems and seeds.