Often time people find areas of moss growing in their lawn and ask what they can do to eliminate it. Moss is a small green plant with finely branched stems and tiny leaves. It produces spores that spread by the wind. Moss forms a thick, green mat on the soil surface. Moss does not kill grass or other plants but instead produces its own food.
When moss is found in the lawn it is an indication that conditions are not favorable for growing grass and the moss is simply filling in the spaces where grass is not growing well. You can attempt to remove or kill moss but unless you determine and improve the conditions so your lawn will grow, moss will continue to return to that spot. There are several conditions that could be encouraging the moss to grow instead of the grass including: too much shade, acidic soil, poor drainage/wet soils, compacted soil, and low soil fertility.
Below is a description of each problem that can contribute to moss growth in the lawn and how to change it:
- Too much shade. Moss can tolerate shade better than grass. There are several options for dealing with shady areas in the lawn. You can plant a more shade-tolerant grass, like St. Augustinegrass, but keep in mind that a deeply shaded area (less than 4 hours of full sun per day) is too shady for any type of lawn grass to grow. If the area is too heavily shaded, you may have to decide which you would prefer, the trees/shrubs or the lawn. If you choose to keep the trees and shrubs you can cover the area under the trees with mulch. If the area is light shade, you can mow the grass in the area at a slightly higher mowing height to encourage deep rooting and allow maximum leaf coverage to intercept as much sunlight as possible for making food. Occasionally, some people decided to let the moss grow in the shady area since it makes a good groundcover that requires little water, no fertilizer, and will stay green year round.
- Acidic soil. Mosses prefer acidic soils and if the soil pH is below what is recommended for grass, this would encourage moss to grow instead. To determine what the soil pH is in an area, you can collect and submit a soil test sample. Soil testing boxes and forms along with information on collecting a soil sample are at the Wayne County Cooperative Extension Office. Most grasses prefer a soil pH of 6 to 6.5, except centipedegrass which prefers a soil pH of 5.5. If you find out the soil pH is too low in the area moss is growing in, you can raise the pH by applying lime.
- Low soil fertility. A soil test will be important in determining if an area where moss is growing is low in nutrients or not. Moss thrives in unfertile soils where grass does not do as well. Along with a soil test to see if the area is lacking in a nutrient, fertilizing your lawn with the correct amount of fertilizer at the proper time will encourage a healthy lawn.
- Poor drainage/wet soils. Moss grows well in wet soils. If the moss is growing in a low lying area where the soil stays wet, improving the drainage can discourage moss from growing. Avoid irrigating on an automatic or regular schedule. This can encourage excess moisture and wet soils. Water your lawn only when you need to. When it shows signs of stress like a dull, bluish-gray cast or when footprints remain after walking through the lawn, it is time to water the lawn. Properly watering a lawn should be to water infrequently but deeply to encourage deep root growth which will tolerant drought stress better than a shallow root system.
- Compacted soils. A lawn does not grow well in compacted soils because it prevents the movement of air, water, and nutrients to the roots. Soil compaction also prevents good drainage allowing a favorable spot for moss to grow instead of grass. Soil compaction can be alleviated by aerification. Aeration is the removal of cores of soil from the lawn. Many landscape and lawn businesses can aerate a lawn or aerators can be rented at many places.
Moss can be a correctable problem by evaluating the area where moss is growing and determining what factors might be preventing a healthy lawn and encouraging the moss. Correcting the problems can reduce and eliminate moss from areas in the lawn.
Jessica Strickland is an Agriculture Extension Agent, specializing in horticulture for North Carolina Cooperative Extension in Wayne County.