Centipede grass is a very low-maintenance warm season grass. Homeowners like it because it can grow in poor soils, even those that are sandy or clay-based. Over time, all grass thins out and should be overseeded to create a thick, healthy lawn. This is done by spreading grass seed over the existing lawn to fill in gaps. Overseed centipede grass in the spring or early summer, when it's early enough in the season to germinate before winter sets in.
Mow the existing lawn low so the centipede grass can make contact with the soil. Remove debris such as weeds and rocks and cut the grass to about 1 inch.
Scratch the surface of the ground to aerate it. Rake until there are loose pieces of dirt. This will also ensure the seeds take root easier.
Fill a broadcast spreader with centipede grass seed. The seed bag will tell you how much seed to use. Spread half the seed throughout the yard then go over the same area a second time with the rest of the seed. Make the second pass perpendicular in direction from the first for uniformity.
Rake the seeds very lightly into the top of the soil. Covering the seeds with 1/8 to 1/4 inch of soil will ensure that the seed has good contact and can germinate easily. Don't cover them with more than 1/4 inch.
Water the seeded area until it's moist. Keep the yard moist until the seedlings germinate. Every time you water, make sure the water soaks 4 to 8 inches into the ground. This will help the seed develop a deep root system. Centipede grass can't tolerate drought like other varieties so deep watering is necessary.
Mow centipede grass once it grows and fills in the bare spots. Keep it mowed to a height of about 2 inches.
Fertilize centipede grass with a food that has higher levels of nitrogen and potassium and a low amount of phosphorus because it reduces iron levels. Look for ratios such as 15-0-15 or 16-4-8, which are both good for centipede grass. Apply, as per manufacturer's instructions, at the time of overseeding and annually after that.