Moss Control in Home Lawns

PP039 (4/00R)

By Dr. Sharon M. Douglas
Department of Plant Pathology and Ecology
The Connecticut Agricultural Experiment Station
123 Huntington Street
P. O. Box 1106
New Haven, CT 06504-1106

Telephone: (203) 974-8601 Fax: (203) 974-8502
Email: Sharon.Douglas@ct.gov

The occurrence of moss in lawns is a common problem for many homeowners. Moss is usually associated with problems with turfgrass management and/or soil and site characteristics. Mosses are small plants that can grow and out-compete turfgrass species when one or more of the following occur: high soil acidity (low soil pH), low soil fertility, shade, poor soil drainage, and soil compaction.

1. Soil Nutrition:
The first step in controlling moss in a lawn is to determine the nutritional status and pH of the soil. Soil samples can be submitted to the Department of Soil and Water for analysis. The test report will make appropriate suggestions for fertilizer and lime applications to correct any deficiencies. When turfgrass species are growing under conditions of poor fertility, they are weak and are therefore unable to compete with encroaching mosses.

2. Shade:
Turfgrass will generally not grow where sunlight is limited or non-existent. At least 3-4 hours of full sunlight or 6-8 hours of filtered sunlight are necessary to grow grass. If heavy shade is a problem, trees may need to be pruned and a "shade" grass seed mix used for the area. When moss is troublesome in grass under trees, there is often little that can be done. In these situations, perhaps shade-tolerant groundcovers such as pachysandra, English ivy, or myrtle should be considered. Although moss is often found in shady spots, it can also grow and thrive in sunny locations.

3. Poor Soil Drainage:
If moss is present in low areas of a yard or if soil drainage is a problem, it is important to determine if and how these problems can be remedied. Drainage tiles can be effective in many circumstances. However, it is important to determined the effects of the excess water on the adjoining areas.

4. Heavy or Compacted Soil:
Heavy soils can be amended by incorporating several inches of sand, compost, or other sources of organic matter into the soil. These amendments may help to improve both soil texture and drainage. Compacted soils can also be aerated. This often requires special equipment that removes small cores of soil to increase soil aeration. Soil amendments with sand or composted leaves as described above may also help.

Strategies for Control:
Moss can be physically eradicated by mechanical removal and hand raking with a stiff-tined rake. However, control may only be temporary if the reason(s) for the infestation is not established or remedied as previously described.

Moss can also be controlled through the use of chemicals. Since mosses usually grow most vigorously during the cool moist conditions in the fall and spring, these are the best times to apply chemical moss killers. Among the compounds registered for use in Connecticut are potassium salts of fatty acids and iron sulfate. Consult the label for dosage rates and safety precautions. Once the moss blackens and dies, it will need to be thoroughly raked and removed before the area can be seeded with lawn seed. However, it is still necessary to correct the conditions so they favor the growth of the turfgrass rather than the moss in order to achieve long-lasting control.

In situations where moss control has been repeatedly attempted without success, it might be prudent to consider alternative groundcovers such as pachysandra, English ivy, and myrtle for the site since these plants thrive under these conditions.

Summary

The occurrence of moss in lawns is a common problem for many homeowners. Moss is usually associated with problems with turfgrass management and/or soil and site characteristics. Mosses are small plants that can grow and out-compete turfgrass species when one or more of the following occur: high soil acidity (low soil pH), low soil fertility, shade, poor soil drainage, and soil compaction. This fact sheet discusses how to avoid and minimize the factors favorable for moss growth.