Mosses, like most lawn weeds, show up and become a problem in lawns all over the United States, and around the world. As some might believe, lawn mosses do not crowd out or kill existing lawn grasses. Moss usually shows up in bare areas of a lawn due to several causes: unsuitable grass varieties, poor drainage causing soil to stay constantly soggy or wet, drought, soil compaction, excessive shade, nutrient deficiencies, diseases, improper mowing, and other cultural practices. Though moss can quickly be killed, the best method for long-term prevention is to treat the cause(s) for its development. In doing so, you'll produce a healthier lawn, and one that is an unsuitable environment for moss.

If you have moss in all or parts of your lawn, it can be killed very quickly with products containing iron and sulfur. I recommend products such as Moss-Out or Hi-Yield Iron Plus. These products don't pose any serious threat to the environment. In fact iron and sulfur are essential nutrients for grasses and tend to improve their color, making them greener. Although these products will kill existing moss, know that unless the underlying conditions are changed, moss or other weeds are likely to reappear.

Poorly adapted varieties of grass may fail due to cool temperatures, inadequate drainage, or prevalent diseases. Poor drainage and soil compaction can cause roots to suffocate or be subject to disease. Thatch and soil compaction can impede water movement to grass roots, leading to drought stress.

Raising the soil pH with agricultural or dolomitic lime can improve availability of nutrients and supply calcium and thus helping the turf grow better, but will not kill moss directly. The following steps will generally control existing moss and discourage it in the future:

• Use a moss control product to kill existing moss, then raking out dead moss

• Skip the moss control product and dethatch or rake out all the moss

• If replanting the lawn, choose a suitable grass type. Your local nursery and garden center professional or extension agent can be of great help!

• If necessary, take steps to improve soil drainage and compaction. Sometimes aeration is enough. Low-lying areas that hold water may need to be graded in order to drain properly. Till in sand, gypsum, or other soil amendments to soften compacted soil and improve drainage.

• If necessary, take steps to provide more light. Thinning limbs, or removing lower limbs, of large trees will often help to allow in more sunlight.

• Do a soil test to identify pH and any nutrient deficiencies. Soil test kits can be purchased or ordered at most local nursery and garden centers, or your local extension office might provide these services for you. Soil test kits, such as the Rapitest, provide instructions for adjusting soil pH to meet the needs of specific types of lawn grasses. Your local nurseryman or extension agent can provide instructions as well. In general, to increase soil acidity, apply chelated iron and or sulfur. To reduce soil acidity apply pellet lime.