The best time to seed a lawn depends on the climate. Cool-season grasses are best planted in the fall, while warm-season grasses should be established in the spring.
Use cool-season grasses like Kentucky bluegrass, tall fescue and annual ryegrass in the northern part of the United States. Fall seeding allows the grass to become established before the hot weather arrives. Spring seeding can work if the grass is planted early enough.
Plant warm-season grasses, including bermudagrass, St. Augestine grass and carpetgrass, in the southern part of the United States. The seedlings need a long period of warm weather to thrive.