Weed seeds can be transported by wind, water, animals, soil amendments, poor quality grass seed, and lawn and garden equipment. Since weed seeds are transported through the wind and air, they can pollinate nearby grounds causing the weeds you thought you had killed to start to grow again. Weed seeds can remain dormant for several years before they begin to grow, considering the need to reach the soil's surface and get proper sunlight and moisture before they germinate. The health of your lawn and its ability to sustain depends on the weeds that have grown and how you choose to respond to them. You are best equipped to fight weed invasion when you can identify common weeds and the ways to successfully get rid of them.