What does overseeding mean?
The laying of grass seed on top of existing grasses to promote new growth or to replace the existing grass with a new strain for a season. Most commonly done by courses that use Bermuda grass, which goes dormant in winter. In the fall, a Bermuda grass course will put down ryegrass (or some other cold season type) seed on top of the Bermuda grass, timed so that as the Bermuda grass goes dormant the ryegrass grows in. Then, in spring, Bermuda grass will be seeded over the ryegrass. Many courses that overseed will close or offer discounted greens fees during these periods because the greens will be heavily sanded and the new grass may not be cut for a week to 10 days.
