Overseeding is an important part of lawn maintenance. Lawns can naturally thin out over time due to poor soil conditions, competition from weeds, insect damage or normal wear and tear. Overseeding is simply adding grass seed to an existing lawn to promote thicker growth that discourages weeds and insects. The cause of lawn problems must be understood before overseeding to make sure the right seed mix and quantity are applied.
Evaluating Your Lawn
Healthy lawns need turf grasses that are suited to the local soil and light conditions. Check your soil for compaction by cutting out a small piece of turf. The soil should be moist and crumble easily in your hand. Compacted soil needs aeration which should also be part of the yearly lawn maintenance routine. Examine the turf for signs of insects such as grubs and other larvae that can damage root systems. You will also need to know how much of your lawn is in partial or complete shade before choosing a turf grass for overseeding.
Turf Grass Selection
Choose a grass seed blend containing endophytes, a naturally occurring fungus that protects grass against many insects and is safe for children and pets. Lawns with a lot of shade can be seeded with creeping red fescue, hard fescue or shade tolerant varieties of Kentucky bluegrass. If compacted soil is a problem, plant a seed mix containing perennial rye grass.
How to Overseed
Before overseeding, cut the lawn to about 1 inch in height and remove the clippings and any other plant debris. Dethatch the lawn if necessary and aerate to allow air and water into the subsurface. Seed the lawn using a spreader to ensure even distribution, carefully following the directions for the amount of seed use. Broadcast spreaders work best for large areas but a handheld spreader will be fine for small patches. Fertilize and water the seeded areas.
When to Overseed
Early fall is generally the best time to overseed as it gives the newly planted grass time to develop better root systems over the winter. Grass planted in the spring will struggle to endure the hot, dry summer conditions. Weeds are also less vigorous in the fall which means less competition for the new grass. If overseeding in the spring is the only option, do so as early as possible to allow the grass to get well established before the summer months.
Establish a yearly maintenance program for your lawn including overseeding. Regular dethatching, aeration and additional seeding will keep your grass thick and rich in color. A naturally healthy lawn will reduce the need for fertilizers and other chemicals. If overseeding a lawn that is already very vigorous, reduce the amount of seed applied to one half of the recommended quantity. Periodically remove some turf and examine the roots and soil for signs of potential problems.