Lawn moss is a common problem caused by poor lawn maintenance practices, moist grass and soil, and poor sun coverage. Lawn moss does not particularly damage a lawn, but it can cause it to look patchy and sickly. Proper lawn maintenance techniques will prevent lawn moss.
Proper lawn fertilization techniques help prevent the growth of lawn moss. Lawns require a lot of nitrogen to grow properly. For the accurate application of fertilizer to a lawn, a pH test of the soil's acidity is recommended. Most university extension services provide pH tests for a small fee. This requires a small sample of soil from your lawn. Results will be returned with recommendations on how best to apply fertilizer to the lawn. Lawn fertilizer will increase turf density and prevent the growth of moss.
According to Oregon State University, poorly draining areas in the lawn are in danger of moss infestation. This is often solved by aeration, the pulling of dirt plugs from the yard. This helps increase the lawn's ability to absorb water quickly and efficiently. Aeration also prevents compaction of soil and removes thatch--dead grass--from the top layer of soil in the lawn. Wet soil increases the likelihood of moss growing.
Aerate the lawn twice a year when the lawn is compacted, in March and September, and decrease to once a year when moss problems are under control.
Proper mowing prevents the growth of moss. Grass cut too short during the summer causes grass to burn away and decreases density. Grass left too long will retain water and will increase moss growth. Grass should be cut regularly to 2 to 3 inches in length. Grass requires cutting using the one-third rule, that only one-third of the grass blade should be cut at a time.
According to the University of Minnesota, clippings from grass cut using the one-third rule decompose without contributing to thatch and provide the lawn with nutrients such as nitrogen and phosphorus, making them a natural fertilizer.