Moss growing in lawns is generally a sign of poor turf conditions. According to Washington State University, improving the soil and growing conditions of the lawn grass will go a long way in controlling moss. In fact providing physical improvements to the soil could eliminate the need for any chemical additives such as herbicides or pesticides to the existing lawn. Improving the lawn to control moss be done any time during the year. The results are most effective while the lawn turf is growing during the summer.
Remove the moss and any lawn thatch by using the thatching blade on the lawn mower. The vertical blades on the thatching blade remove the moss and other dead organic debris just under the lawn's grass blades. There are various types of thatching blades on the market. Follow the directions from the specific manufacturer for installation and operation of the device.
Rake the thatch from the lawn using a garden rake. The vigorous action from the rake's tines will improve the soil through aeration. Place all thatch material in a compost pile.
Seed the area with a turf-type ryegrass seed. Follow label directions on the seed package for distribution and seeding rates. The ryegrass seed will be fast growing. The goal is to choke out any remaining moss from the lawn.
Cover the newly planted grass seed with up to one-fourth inch of sterile potting soil or sand.
Water the seed with the garden hose and sprinkler. Keep the seed moist but not overly wet. In other words, do not put on so much water that it makes puddles.
Apply a moss herbicide in the early spring or late fall when the moss is thriving as a last resort. Follow all label directions when using an herbicidal product since some of the existing turf grass could be damaged by the chemical. The herbicide is only part of the solution since the lawn grass must still be planted.