While moss can be killed, it will simply return time and time again if the conditions in the area do not change. The best way to deal with moss is to take steps to actively control it. By managing your lawn and garden in a way that will discourage the growth of moss, you can create an environment that moss no longer finds desirable, and will not return to.
Fertilize your lawn. Poor fertilization is a common cause of poor lawn growth, which in turn makes room for mosses to take over the area. Apply lawn fertilizer two to four times a year. Always apply fertilizer during the growing season, not when the lawn is dormant for the winter. Apply a more nitrogen rich fertilizer in the early spring. Use a lighter application with less nitrogen in the fall.
Locate areas with poor drainage. Wet, soggy soil is an ideal breeding ground for moss. The best way to improve drainage is to aerate your lawn. Use a punch-core lawn aerator to remove clumps of soil. This will help compacted ground drain better. If the lawn still seems too wet, try top-dressing it with a blend of compost and topsoil or compost and sand. This should help the lawn drain away excess water better.
Thin out thick trees so that the plants and grasses beneath them get enough sunlight. Use pruning shears to remove small shoots. Remove dead branches and thin out the top of the tree with a pole saw. Remove low hanging branches with a folding hand saw or bow saw. Once a little more sunlight is allowed to get through the tree, the ground beneath will be drier and the grass will grow thicker, creating a lush, healthy environment that moss will not grow in.
Plant shade-friendly plants and grasses in shady areas of the lawn. Areas with the least sunlight are the most likely to experience moss growth. A mixture of Kentucky bluegrass and fine fescue is ideal for shady conditions. St. Augustine grass also does well in this type of area. It may be impossible to increase the amount of sunlight that is available to every part of the yard. Shade friendly plants will take up space that may otherwise get claimed by moss.