Dandelions are a broadleaf perennial that can grow in any soil and are most numerous in full sunlight. In the early spring, new sprouts will emerge from the taproot, which can be 2 to 3 feet deep in the soil. They grow yellow flowers that mature and turn into white puffballs that contain seeds which spread with the wind to other lawns. Even though they disappear in the fall, the taproot survives deep in the soil to start the cycle again in the spring. To keep dandelions out of your yard, this root has to be killed.