Overseeding is a lawn cultivation tactic which is designed to keep a lawn thick, healthy, and lush by adding new grass seeds. The young grass plants which germinate from these seeds will compensate for the death of older plants, reducing the risk of the development of a straggly, patchy lawn. One of the best times for overseeding is in early fall, although certain warm season grass cultivars should be overseeded in the spring, and it may need to take place on an annual basis in some regions of the world.
It's time to overseed a lawn when the lawn is starting to look a little bit tired. Thinning and bare patches may be emerging, the grass may be growing more slowly than it did in the past, and the lawn may have a slightly unkempt look despite routine mowing and other forms of care including dethatching, aeration, and fertilizing. It is a good idea to confirm that a disease process is not ongoing before overseeding; if the changes are rapid, it can indicate disease rather than the natural passage of time. Some gardeners also like to take a soil sample to determine which nutrients may be needed by the lawn before they overseed.
The overseeding process starts with mowing as low to the ground as possible, and then raking the soil. Raking removes clippings and other debris, and helps to break up the soil so that the grass seeds will be able to thrive. At this point, the lawn may look especially dire, as it is cropped so close to the ground. The goal is to ensure that the grass seeds fall on soil, where they can germinate, rather than on matted organic material and debris, which will inhibit germination.
Once the site is prepared, grass seed can be spread, and the lawn can be provided with supportive watering and fertilization to encourage the grass shoots to grow. They will be well established by winter, putting out a flush of lush new growth in the spring.
It is a good idea to use a blend of grasses when overseeding, as this will increase the hardiness of the lawn, in addition to creating more visual interest. Overseeding should not be performed if more than half of the lawn has become bare; in these cases, the entire lawn should be taken out and the site should be prepared for a fresh seeding or installation of sod.
