Moss is one of the most common and annoying of all lawn weeds. Moss seems to plague any lawn areas that are shady and damp—precisely those areas where desirable turf grass seems shy about growing thick and full. There are many thousands of species of moss, but they are all relatively primitive plants with tiny leaves that are only a single cell thick. Rather than seeds, these plants reproduce through spores, and because mosses are structurally much different than vascular weeds, they do not respond to the same control methods. Many mosses have existed almost unchanged for millions of years, which is an indication of how adaptable and tenacious they are.
Mosses are very shallow-rooted plants, so immediate removal is not particularly hard. But permanent control of moss is mostly about changing the cultural conditions that favor their growth.
Before Getting Started
If you want to eliminate moss, it's essential to know why it's there in the first place. There are many reasons why moss appears in a turf-grass lawn, all of them cultural:
- Low soil pH (acidic soil)
- Low nutrient levels in the soil
- Poor drainage and damp soil
- Excessive shade
- Compacted soil
It should be noted that these conditions are precisely those that make it hard to grow desirable turfgrasses. Thus, one of the best means of moss prevention is to create conditions where grass can thrive. While it's possible to temporarily eliminate the moss growing in your lawn, it will only reappear unless you identify and correct the conditions favorable to its growth.
When to Get Rid of Moss
Moss can be attacked whenever it appears. It is relatively easy to eliminate temporarily at any time of the year. However, for the longer-term solutions involving changing the cultural conditions of your lawn, focus your efforts on the normal times for grass care—especially the spring and fall.
The ingredients in commercial moss killers—most contain iron sulfate and ferrous ammonium sulfate—are not physiologically toxic in the way that other herbicides are. But they are corrosive substances that can badly irritate skin and lungs. Further, run-off chemical from these products is seriously hazardous to aquatic life. If you must use these herbicides, apply them as spot treatments directly to patches of moss, and never spray them on concrete and other surfaces where run-off is likely.
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Not all these supplies are necessarily required, but some of the tools and materials you may need include:
Equipment / Tools
- Garden (bow) rake
- Dethatching rake or power dethatcher
- Soil aerator (where needed)
- Pruning saw (where needed)
- Garden sprayer
- Baking soda
- Dish soap
- Chemical moss killer
- Soil amendments (as recommended)
- Lawn fertilizer
Rake Your Lawn
Since moss is shallow-rooted, you may be able to rake it out. A good brisk raking with a bow rake or even a leaf rake may pull the moss from the soil. This will work best when the lawn is moist, such as after a rainfall or lawn watering. Raking several times from different angles is the best way to loosen moss from the soil.
Try an Organic Solution
For homeowners who are loath to use synthetic chemicals, there are several very effective organic, non-toxic remedies you can try. For example, you can fill a garden sprayer with 2 gallons of lukewarm water and mix in a box of baking soda, then spray this solution on the patches of moss.
Another remedy is to mix ordinary dish soap (Dawn Ultra is a preferred product) and water in a garden sprayer (5 ounces per gallon of water). This mixture will quickly kill moss.
Finally, there are commercial horticultural soaps, such as Safer brand, that will also kill moss.
Spray With Chemical Moss Killer
The popular herbicides used against many weeds are not very effective against moss. If you do want the quick action of a chemical, choose a targeted product containing iron sulfate or ferrous ammonium sulfate, mixed according to label directions (usually about 1 ounce per gallon of water). Such products are usually labeled as "moss killer."
Remember, though, that chemical moss killer is by no means a long-term solution. As soon as the chemical drains through the soil or runs off (with the accompanying hazards to groundwater and aquatic life), the area will once more become overrun with moss unless the underlying conditions are corrected.
Remove Thatch and Aerate the Lawn
With surface moss removed, your efforts can now turn toward preventing future moss growth. The first step here is to evaluate the role that thatch buildup might be playing. Some homeowners intent on getting rid of moss really need to be focusing on getting rid of thatch, which can prevent water from draining properly through the soil.
The process of removing thatch is called "dethatching." Hard manual raking with a sharp-toothed bow rake or a special dethatching rake will do the job, but many people prefer to hire a professional service or rent a power dethatcher to do this labor-intensive job.
Following up dethatching with annual aeration will help reduce soil compaction and improve drainage and air circulation, which makes the soil more conducive to grass and less friendly to moss. When to aerate depends in part on the type of lawn grass you grow. Aerate cool-season grasses in early fall and warm-season grasses in mid-spring to early summer.
Indeed, the best defense against moss is a good offense. Healthy grass will crowd out weeds. Instead of asking, "How do I get rid of moss?" the better question is "How can I make my lawn healthier?"
Getting rid of moss in a lawn can simply be a matter of addressing the issue of excessive shade. Open up the area to more sunlight through tree removal, or by having some of the larger, lower branches pruned off. Most grasses do best with six hours or more of direct sunlight per day, though some shade-tolerant grasses will accept three or four hours. In your tree pruning, strive to provide sunlight in those amounts.
Increasing sunlight will also help improve the health of any garden areas on your property.
Evaluate Your Soil
Moss infestations are very often traced to poor soil conditions—especially pH and nutritional problems. A great way to begin your investigation is to send in a sample of your soil to your local Cooperative Extension service so that they can test it for you. Tell them that you are trying to get rid of moss in a lawn, requesting information on soil pH and nutrient content.
Moss-infested lawns often have acidic soil. It's not so much that moss likes acid soil, but rather than turf grasses react badly to acid conditions. But don't amend the soil with agricultural lime (an alkaline powder that will reduce acidity) unless the soil test indicates a need for it. The soil test may have other recommendations for how to best adjust the soil pH, such as topdressing with wood ash.
Finally, the soil test will give you valuable information on the nutrients in your soil, making recommendations for fertilizers and other amendments to add in order to make it suitable for growing turfgrass.
The soil analysis report may also alert you to possible drainage problems caused by high clay content. Water tends to percolate slowly through overly clayey soils, and that can lead to visible puddling. The soil test can confirm that the clay content is high in your lawn. This kind of drainage issue can be corrected by regularly amending the soil (for example with humus or another organic material) to make more friable.
Poor drainage can be caused by other factors in addition to clay content. If the lawn receives a lot of foot traffic (as when children play on the lawn frequently), your problem could be soil compaction—a problem that can be addressed by more frequent lawn aeration.
Some serious drainage problems occur when the underlying subsoil is very dense and impermeable, which occurs in regions where a hardpan layer lies below the topsoil. Poor drainage in these situations may need to be addressed by changing the contours of the yard to help excess water drain away, by the installation of a French drain, or even by digging up the entire lawn to change the composition of the underlying subsoil. Such radical remedies are rarely needed, however, if all other solutions are tried.
Plant Different Grass Species
Moss is opportunistic and will sometimes fill in lawn areas left bare because the grass variety that you have chosen is ill-suited to shady conditions. Here, the solution to the problem may be as simple as switching grasses. Tall fescue grass, for example, is a relatively shade-tolerant grass that may crowd out moss once it becomes established.
Switching grasses can be done all at once, by killing of the existing lawn, then planting a new lawn by seed or sod. But it can also be done simply by repeated top-seeding using shade-tolerant grass seed. Make sure to loosen the soil in bare spots and areas where moss has taken hold, and sprinkle new seed over these areas. Over a year or two, these areas will flourish as shade-tolerant, moss-resistant lawn space. After planting, follow recommended care procedures, especially when it comes to fertilizing. Healthy, dense grass means little or no moss.
Remember, though, that no turfgrass species will thrive in areas of total dense shade. Unless these areas get three or four hours of sunlight or bright filtered light, it may be better to plant an entirely different ground cover plant, which will also have the effect of blocking out moss growth.