Most lawns around Ashland, Mechanicsville, and Henrico are tall fescue. It is a cool-season grass, which means it loves October and hates July. Every summer it thins, and every fall it needs help filling back in. That help is core aeration and overseeding, and timing is everything.
The window is roughly mid-September through late October. Soil temperatures are still in the 60s, so seed germinates in a week or two. Nights are cooling, so new seedlings are not cooked. And summer weeds like crabgrass are dying off, so the new grass is not competing for light.
Aeration matters because our soil is clay. A core aerator pulls thousands of plugs out of the lawn, opening channels for water, air, and seed to reach the root zone instead of sitting on top of compacted ground. Seed that falls into an aeration hole has far better soil contact than seed broadcast on a hard surface.
Spring seeding sounds logical but usually fails. Seedlings that sprout in April have about eight weeks before heat and drought arrive, and pre-emergent weed control applied in spring will stop grass seed too. Fall seedlings get seven months to root before their first summer.
After seeding, water lightly every day for two weeks, then taper. Skip the first mow until the new grass is three inches tall, and stay off the lawn as much as you can. Do that, and the thin patches from August will be gone by Thanksgiving.