Many of the areas of your lawn that might appear thin and weedy in the spring will thicken naturally in the coming months. By late summer or early fall, areas that might still be thin will be evident. Fall, by the way, is generally the best time for seeding. Large bare areas, six inches or more in diameter may require seeding in the spring. We also offer a service that combines core aeration and overseeding to fill in lawns.. Please contact your Field Service Professional for recommendations about seeding your lawn.