A green, healthy, weed-free lawn speaks multitudes about its caretaker. In climates with mild winters, moss and crabgrass can easily fill in areas where a lawn is dormant, causing substantial work for gardeners in the spring. Prevent unwanted plants from growing in your lawn with overseeding, the process of covering a dormant lawn with temporary winter grass. The most commonly used winter grass is perennial rye grass.
Dethatch the lawn with a dethatching tool. Manual dethatching tools look similar to a rake, but have sharp hooks at the end to cut through and pull up the thatch. Manual thatching is best for lawns smaller than 1,000 square feet, as they require a great deal of upper body strength. Power rakes are a mechanical dethatching tool that homeowners simply run across the yard, but they are exceptionally strong and tend to pull up some of the old lawn along with the thatch.
Rake and remove the thatch from the lawn. If you compost, mix the thatch into the compost pile.
Fill your manual seeder with half of the seed and cover the entire yard. Fill your mechanical seeder again and cover the yard, going in a perpendicular direction. For instance, if you initially seeded from north to south, seed the second time from east to west.
Rake the entire yard with a stiff broom. This will mix the seed into the soil, ensuring optimal contact.
Fill your manual seeder with starter fertilizer and spread it over the entire yard.
Fill your manual seeder with pre-emergent crabgrass herbicide and spread it over the entire yard. Check with your garden supply store to verify that the herbicide will not kill off either species of grass, the summer grass or the new seed. Pre-emergent herbicides kill the crabgrass while it is still germinating in the ground, eliminating the problem.
Irrigate the lawn with 2 inches of water. Irrigate enough to keep the soil moist until the seeds germinate, then reduce the watering to every other day. If the ground is not drying out within that time, reduce watering to every three days.