Every authority states unequivocally that the fall season is the best time to seed grass, preferably in September after the hottest months are over and when there is a good amount of moisture available. If you seed in the fall the grass will thrive, nevertheless, the heaviest sales of seed are in the spring.
If you do have to seed in spring start as early as the weather will permit so that there will be a good amount of root growth started before the hotter weather set in. May plantings usually suffer from heavy competition with crab grass and other summer weeds as well as from heat and inadequate amounts of moisture.
Usually, where seedings are necessary in late May or during the summer, it is best to make a temporary lawn of rye grass, and then turn this cover under for permanent seeding in early fall.
Grass seed is relatively small and must not be planted deeply. Cover larger seeds such as rye grass and chewings fescue with soil to provide enough contact with the moist soil for germination and growth. Small seeds such as the bent grasses need only partial covering in moist seasons. You will need four pounds of seed for each 1,000 square feet of lawn; heavier seeding will not make up for poor-quality seed or a poorly prepared seedbed as it merely causes an excess of competition between seedlings.
If possible, use a mechanical spreader. Whether you are sowing seed by hand or by spreader, sow by dividing the seed, spreading part in one direction, the rest crosswise to the first. This insures even coverage and reduces the chance of missed spots or windrows. Rake the seed lightly, or drag a flexible steel doormat over the area. Then roll lightly to firm the seed into the soil. Small lawns may be top-dressed with 1/8 inch or so of screened soil or compost. more click how to choose a grass for residential lawns
Slopes require special treatment as new seedings are likely to be washed by heavy rains. You can use straw to cover them, but it must be picked up as soon as the grass gets started. Or the new seeding can be promptly covered with open mesh burlap or cheesecloth or a special garden-supply stock of open mesh cloth that can be left in place to rot and become part of the soil. This prevents soil erosion and keeps the soil surface moist, protecting the young seedlings from damage by exposure to the sun. Ordinary burlap should be removed when grass sprouts are 1/2 to 1/4 inch long.
Natural rainfall is best for new seeding, but if the weather is dry it is necessary to water for prompt germination. Do your watering in the morning, with a fine mist-like spray to avoid puddling or crust formation. Once the seed has started to sprout, the moisture supply must be constant or the plants may die.
For level places use a sprinkler and get the soil wet at least 5 inches with each watering, but don’t keep watering until the soil is waterlogged and too compact. For slopes use a drip hose, or wrap the hose in porous canvas, so that the water will ooze out slowly in big drops and go off into the soil quickly.
Seed mixtures in new plantings develop unevenly. The “nurse” grasses (such as rye grass), and the semi-permanent types will grow rapidly. To prevent their damaging the slower-starting permanent grasses, such as the bluegrasses, by their shade or competition for moisture and soil nutrients, begin mowing when the tallest grass is 2 inches. Do not mow shorter than 1 1/2 inches.