About Moss
A mossy lawn doesn't kill the grass but conditions that encourage its growth can. Moss is a symptom of an environment that isn't right for turfgrass, so simply removing it only provides a temporary solution. Improving the conditions so they favor the growth of grass is a more effective method of getting rid of moss.
There are several conditions that give moss an opportunity to spread and prevent grass from becoming established. Find out which ones are affecting your lawn and correct the problems.
Acidic or Infertile Soil
Use a soil tester to determine if it's suited to your grass. Soil that's too acidic (has a low pH level) will hamper the growth of grass. Moss, on the other hand, does well in acidic soil. In general, turfgrass needs a pH level between 6.0 and 7.0. Apply amendments as indicated by the test results to bring your soil to a level that'll better suit your grass. Lime will raise the pH level, making the soil less acidic. Read Test and Improve Your Soil for more information.
The soil test also tells you what kind of nutrients you can add to improve soil fertility. When grass doesn't have the right amounts of nitrogen, phosphorus and potassium, moss will have a better opportunity to grow. Apply fertilizer to add the needed nutrients. Some fertilizer formulations include moss-control ingredients. Read Fertilize Your Lawn to learn more about feeding your grass.
Poor Soil Conditions
Soil compaction and excessive thatch make it easier for moss to encroach upon your lawn. These conditions restrict the movement of oxygen, water and nutrients to grass roots and contribute to poor drainage. Aerate and dethatch your lawn as necessary; dethatching will also remove moss that's already established. See Aerate Your Lawn and Remove and Prevent Lawn Thatch for details.
Excessive Shade
Excessively shady areas benefit moss more than grass. You can prune trees and shrubs to allow more sunlight to reach the lawn. See How to Prune Trees and Shrubs for instructions. Another option is to establish shade-tolerant grass varieties like fine fescue, St. Augustine or rough bluegrass. Ground covers like sweet woodruff, periwinkle and pachysandra are other good options for shady spots. You can also read our guide on How to Grow Shade Grass for ideas on making the most of these areas.
Too Much or Too Little Water
The wrong amount of water will encourage moss growth and discourage the growth of grass. You should water your lawn only when necessary to supplement rainfall. Use a rain gauge to monitor the amount of water your lawn gets and look for signs of drought stress in your grass — like wilting, dull color and grass — that doesn't spring back after you walk on it. A brown, dormant lawn is another indication but if you begin watering a dormant lawn, you'll need to maintain irrigation through the season.
Grass can thin out during a period of drought and give the moss a chance to establish itself when cooler weather and rains return. On the other hand, too much water will make the soil too moist for grass and encourage moss growth. See Watering Tips for strategies to keep your lawn properly irrigated.
Inadequate drainage contributes to the problem of too much water. Improving the grading of your lawn, filling in low spots, aerating and dethatching your lawn can all improve drainage. If necessary, you can install a drainage system. See Solve Simple Drainage Problems to learn more.
Other Lawn Stresses
Lawns that are injured from other stresses will also be susceptible to moss growth. Insects, disease, excessive foot traffic and damage from pets make it difficult for turfgrass to grow. Moss can also begin filling in bare spots in your yard. You can read Troubleshoot Lawn Damage and Diseases to learn to identify and treat these conditions. Mowing too low will also damage the grass and provide an opportunity for moss growth. Read Lawn Mowing Tips: How to Mow Your Lawn Correctly for tips on good mowing techniques.
How to Kill Moss in Your Lawn
Once you've addressed the conditions that led to moss growth, you can remove existing moss with a rake or a dethatching blade installed on a mower. Adjust the mower height so the flexible blade tines just touch the surface of the soil to strip away the moss. It may take several passes to get it all up. After you've displaced the moss, remove it from the lawn. It's unlikely you'll be able to remove all traces, since spores and small pieces of moss will remain in the soil. If you haven't addressed the problems that lead to the growth of the moss, it'll become established again.
Products containing potassium soap, fatty acids or ferrous sulfate dry out moss and can also be used as a moss killer for lawns. Follow the application and safety instructions. Once the product has had time to work, rake up the moss.
Ferrous sulfate can stain concrete sidewalks, driveways, patios and other surfaces, so apply it carefully and sweep up any excess or spills.
When using lawn treatments or lawn-care products, always follow package directions regarding proper clothing, protective equipment, application procedures and safety precautions.
Lawn Repair and Renovation
Now it's time to establish new turfgrass. If you removed small patches of moss, simply seed the bare areas. See Repair Bare Spots in Your Lawn. If the conditions that allowed the moss to become established have severely damaged your lawn, you may need to start over. Read Remove a Lawn to learn several methods for getting rid of your existing lawn. See Seed Your Lawn: How and When to Plant Grass Seed for tips on selecting grass and instructions on starting a new lawn. Alternatively, this might be a time to consider something different. Take a look at Lawn Alternatives for some low-maintenance landscape options.
Moss as a Lawn Alternative
Allowing moss to become established is one alternative if removing it permanently requires more effort than you want to invest. If conditions in your lawn favor moss, you can take advantage of them. A moss lawn provides low-effort, year-round green for your landscape and can do well where grass struggles. If your lawn is failing but moss is thriving, you can remove the lawn and let the moss take over. This is the simplest method. You can also transplant moss using the steps below.
Many mosses don't tolerate traffic well. You may need to install walkways or pavers to direct foot traffic.