The life cycle indicates the time frame that a plant is alive. The life cycle starts with seed germination, and then progresses through a seedling stage, then a period of vegetative growth, then flowering, then maturation of seeds, and finally death of the plant. Annual weeds complete the life cycle in less than one growing season. Any practice that completely removes the shoot or dislodges the entire plant should result in complete kill. Summer annuals and winter annuals grow and compete at different times of the year.
Summer annuals germinate in spring and summer and then mature in late summer and fall.
Winter annuals germinate in fall or winter and then mature in spring and early summer Summer annuals compete most in spring-planted crops before canopy closure or in perennial crops when loss of stand occurs. Summer annual broadleaf weeds include pigweeds, cocklebur, lambsquarters, jimsonweed, ivyleaf and tall morningglories, common and giant ragweed, and velvetleaf. Summer annual grasses include large and smooth crabgrasses, foxtails, shattercane, fall panicum, barnyard grass and witchgrass. These include common chickweed, henbit, most mustards, downy brome and cheat. The growing points on young annual grasses are at or just below the soil surface while the growing points on annual broadleaves are elevated above the soil surface.