Annual weeds persist from year to year by a rapid life cycle from seed, to flower, to seed again.
With some varieties, this cycle may repeat itself several times during a single growing season. With equal speed these seeds ripen, and are quickly redistributed throughout the garden to begin the cycle again. Most annual weeds are easily spotted because the seedlings will suddenly appear in a cluster or group, near where the parent plant grew. Generally, annual weeds will have a fibrous root system which spreads just beneath the soil surface, unlike the fleshy tap roots of the perennial types. This shallow rooting makes them particularly easy to eliminate in the seedling stages.