Moss invading lawns and other turf areas is a common problem this season. Keep in mind that moss is not likely to invade or crowd out grasses in a healthy stand of turf. In general, mosses are not the cause of turf decline but a symptom of environmental conditions or management levels that are unsuitable for supporting quality turf. Mosses may invade turf environments that feature any or a combination of the following conditions:

• low soil fertility
• poorly drained soils
• compacted soils
• excessive shade
• poor air circulation
• high humidity

Poor turf-care practices are another cause of moss problems. General neglect, irregular mowing, lack of fertilizer, and overwatering are common problems leading to poor turf growth, which can, in turn, lead to moss problems.

Mosses are small, primitive, leafy, green plants that develop fine, tangled mats over the turf surface. There are more than 13,000 species of mosses, approximately 50 of which can be found in lawns. Mosses are not always found in low pH soils; some mosses are commonly found on alkaline soils. Adding limestone is a common “remedy” mentioned for moss control but is not suggested unless a soil test has shown the pH needs to be raised. Many soils in Illinois have high pH values; adding limestone will make this pH go even higher, creating more problems for the turf.

Cultural Controls for Mosses. Any cultural practice that encourages proper turf growth and development should be employed to control moss. Evaluate the site and make all necessary corrections to favor turf growth. Specifically, for encouraging turf growth and discouraging moss growth:

• provide adequate soil drainage
• prune trees to allow more light to reach turf
• improve air circulation over the turf site
• reduce soil compaction using cultivation (core aerification or slicing) where appropriate
• maintain adequate soil fertility for the type of grass growing on the site and for the type of
• site (i.e., sunny or shady)
• avoid excessive irrigation
• avoid short mowing (mow as high as use of site allows)
• control thatch
• grow turfgrass species/cultivars best adapted to the setting disrupted by moss

Eliminating Moss. Moss can be eliminated, at least temporarily, by hand raking when it first appears. Ferrous ammonium sulfate or ferric sulfate (iron sulfate) can also be used to control moss. The moss will temporarily burn away but tends to return fairly quickly unless the environment and/or turf management program is altered. Focus on the cultural options listed above for a more permanent answer to moss problems in turf.