Overseeding means sowing seed into an existing lawn to increase the number of grass plants per inch over the turf area. It does not require that you dig up your existing lawn. If you have less than 40% weeds in the lawn, take care of these first. Then simply mow the existing grass very short and then sow the new seed right in amongst the stubble of the existing live grass plants. They act as a mulch to hold the seed in place. As the new seed germinates and grows, sprouts fill in thin spots and bare areas of the lawn, denying weeds an opportunity to return and take over.
It takes only two days--10 days apart--to properly overseed a typical 6000 square foot lawn. You may choose to do only parts of your lawn which will take even less time. Optional steps such as aerating and mulching plus the essential followup watering take some more time, but the entire project is relatively simple and easy to do.
Overseeding has never been a common lawn care practice for homeowners, yet professional turf managers routinely overseed their athletic fields and golf courses almost every year. Although your lawn may not get the workout that golf courses, parks and athletic fields do, it can benefit enormously from overseeding.
Advantages of overseeding are:
Overseeded lawns look greener and are denser.
Thicker turf discourages the germination of weed seeds.
Modern grass varieties add increased resistance to disease.
Newly sown grass revives a lawn of tired grass.
Diversity of grass varieties makes a healthier lawn.