Chemical Control of Moss in Lawns

Jim's MowingMoss in a lawn is an indication that the turf is not growing well. It is important to consider that moss does not kill the grass; it simply creates unfavourable growing conditions such as shade, poor drainage, poor fertility or compacted soil.  These conditions, not the moss, ultimately cause the grass to die out.  If you want to eliminate moss from a lawn, focus on improving conditions for growing grass, and don’t worry about the moss — it will disappear on its own as the grass gains vigour.

Herbicides and chemical control have only short term effects on moss. If herbicide use is not accompanied by proper environmental and physical controls, then the initial effect will be bare dirt or mud. Mosses will eventually return because the lawn deficiency, which led to the moss invasion, still exists. When herbicides alone are used, the symptoms, not the cause, of a weedy lawn are being treated. Furthermore, many of the common herbicides, such as glyphosate, are ineffective against mosses, at least in some conditions. Therefore, if you perceive the moss in your lawn as a problem, improve conditions for growing grass, rather than using herbicides.


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Lawn area with poor vigour of grasses and mosses in the open spaces

Ferrous sulphate, Ammonium sulphate and Copper sulphate

Iron sets back mosses while having little effect on the grass.  However, iron will not always kill the moss. It may “burn” the moss severely and render the plant very weak. If the moss is to be eliminated, it must be removed and grass seed sown into its place for a thick turf. Even so, if the conditions that favor the moss are not changed, the moss will recover over time, and it will not look like an application was ever applied.

Moss can be controlled with products containing Iron Sulphate, and Ferrous Ammonium Sulphate. A good mixture is approximately 3 ounces of Iron Sulphate in 5 gallons of water.  A five-gallon mixture should be sprayed over a 1000 sq. ft. area.  Products such as Moss-Out  (ferrous ammonium sulphate) can be used to control moss.  Note that it is best to keep the Moss-Out product away from sidewalks and driveway concrete, because it will stain the concrete.

Moss can also be controlled by spraying with copper sulphate at a rate of 2 to 5 ounces in 4 gallons of water. The 4 gallons will be sufficient to cover 1000 square feet. However, the material could stain your hands and clothing, and may be caustic to metal containers.  None of these materials pose serious threats to the environment; in fact Iron and Sulphur are essential elements for successful plant growth.

You could also contact Wet & Forget or Agpro both of which have product available that will control moss etc in most situations


Lime is a good product to control acidic conditions in your lawn. Over time, the acidic conditions can become detrimental to grass health by binding up the availability of important nutrients. By liming the turf, especially with a calcium-based lime, one can neutralize the acidity, building a better lawn and a stronger competitor for weeds and moss. The ideal soil pH for most lawns is ‘neutral’, about 6.5 to 7. A pH below 6 is considered ‘acidic’ and over 7 is ‘alkaline’. Acid soil will often be associated with poor fertility, and may encourage moss growth in bare areas.  Limestone is the common remedy used to ‘neutralize’ acid soils. If test of your lawn show pH 4 or 5, then applying limestone twice each growing season, in addition to regular fertilizer applications, should significantly improve the pH level. Do not add lime to control a moss problem unless a soil test indicates a need for lime.

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Poor soil fertility can be a cause for lawn moss growth.  If moss grows in areas of your lawn that appear dry and sunny, then the appearance of moss is probably caused by poor soil fertility.   To see if low soil fertility is contributing to a moss problem, take a representative soil sample from the areas where moss usually grows and have it tested. If tests show deficiencies in certain nutrients, addition of those nutrients could alleviate the problem. Only apply fertilizers if it is needed. Over fertilization can cause other problems, including pest infestations and possibly groundwater contamination.  At the same time your moss problem remains unaffected if low soil fertility was not   the cause to begin with.

Fertilization with a high nitrogen fertilizer can have a significant effect on moss reduction, and supports the growth of healthy turf. Monthly applications of iron and potassium, in combination with nitrogen, are also helpful.  Specific moss control fertilizers are available that contain nitrogen, potassium and iron. These are most effective in a four-application per year program, with applications in early spring, late spring, mid-summer, and early fall. As with all fertilizers, carefully read and follow the directions on the product.

For all of your gardening and landscaping needs call Jim’s Mowing on 0800 454 654 or book online today!

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