Moss, according to the Clemson University Cooperative Extension Service, is a nonparasitic green plant with thread-like stems that acts as leaves. Moss is produced by spores. It does not actually kill grass in lawns but fills in the holes where grass is patchy. Although nonobtrusive, moss is not particularly appealing and needs removal if you find its appearance unsightly.
Moss thrives and tends to grow in shady areas that grass does not grow in. The Clemson Extension Service recommends planting a shade-tolerant variety of grass in the area to cover as much surface as possible. Mowing grass at the top of its recommended height encourages deeper roots and thicker growth, preventing the development of moss. Covering the area with mulch or removing the branches or other obstruction that makes the areas shady will reduce moss growth.
Virginia Cooperative Extension recommends removing the moss physically by raking it to break up moss particles. Removal of the surface moss will not likely destroy all the moss in the area, as spores continue to live in the soil. Collecting all pieces of moss, scratching the surface soil then replanting the area with a turf grass prevents further moss growth.
Grass prefers a soil acidity, or pH, of between 5.8 to 6.5. A lower soil pH will decrease grass production and will allow areas for moss growth. If the soil is too acidic, lime is required to reduce the pH. If the acidity is too low, proper fertilization will encourage better grass growth, according to the Virginia Cooperative Extension.
Moss grows in both well-draining and poorly draining soil but is more likely to grow in soil that retains too much water. Altering the trenching of the area to collect excessive water, installing French drains or digging a sump are all possible solutions. A French drain is a ditch dug at a slight slope and covered with gravel. The ditch drains water away from areas that easily flood to a safe location. A sump is a low place in the lawn that collects water, such as a covered hole. Adding organic material to the soil to increase its aeration will improve the soil quality over time, preventing poor drainage issues.
Compacted soil prevents the roots of grass from developing deeply in the soil. This prevents grass from spreading properly. A 1/2- to 3/4-inch metal pipe plunged 4 to 6 inches into the soil will pull out a soil sample. If the roots in the soil are shallow upon examination, the soil is likely compacted. Running a core aeration machine over the lawn in both a north to south and east to west direction will relieve compaction by removing small plugs of dirt from the soil. A core aeration machine has rotating metal blades with small probes attached to the end. These probes remove plugs of dirt from the lawn as the machine is pushed forward. This increases aeration and grass growth.