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I Have Moss in My Lawn – What is it?

  • Mosses are plants, but are not vascular plants, which means they have no system for carrying water from the soil to other parts of the plant
  • Mosses have no roots, just root-like stem extensions underground which must be close to a source of moisture.
  • Mosses reproduce from spores or vegetative parts
  • They are able to manufacture their own food. They are not dependent on sunlight for photosynthesis as turf grasses are.
  • Moss can be found virtually anywhere, even in full sun if enough moisture is present.

Why Does My Lawn Have Moss?

  • Moss is a symptom of lawn problems, not a cause of them!
  • Site conditions that favor moss are usually poor for healthy grass growth.
  • Moss can be present when the lawn is stressed by one or more of these common problems:
    • Shade
    • Soil acidity
    • Poor drainage
    • Soil compaction
    • Low fertility
    • Thin turf, bare areas
    • Drought
  • Shade – a healthy turf requires several hours of direct sunlight each day. Filtered light can support good lawn growth if enough light is getting through. Since moss does not depend on the sunlight for ‘food’ it can get established in the densest shade.
  • Soil acidity – Under acidic soil conditions (below pH 6.0) turf grass growth suffers and nutrients are less available for turf growth
  • Poor Drainage – when the soil is too wet, the area around the roots can stay soggy which inhibits healthy root growth of turf grass. Over watering a lawn can also cause this condition.
  • Soil Compaction – compacted soils reduce drainage. In addition, the roots of the grass plants can have trouble growing properly in compacted soils.
  • Low fertility, thin turf – a lawn that is deficient in nutrients will not grow as vigorously and can thin out, giving the moss an advantage.
  • Drought – unirrigated lawns can go dormant and thin out during the summer months. When fall rains come, these lawns may not recover fast enough to compete with moss growth.

** All of these lawn problems can stress the turf, which reduces growth of the grass. When conditions are favorable, moss can move right on in! **

How Can I Control the Moss?

A combination of cultural practices and chemical control can be used to effectively control moss. Chemical control alone is rarely a long-term solution since moss is often a symptom of other lawn problems.

Cultural Practices:

  • Reduce Shade – shade keeps moss from drying out and shade can weaken a lawn. Do whatever you can to minimize shade and increase the amount of direct sunlight to your lawn. Remove or limb up trees, trim back shrubs, etc.
  • Lime applications – Lime (Dolomite, Dolopril agricultural limestone, calcium carbonate) will raise the pH of the soil. Low soil pH (acidic) promotes moss growth and reduces availability of nutrients to grasses. Applying lime does not have a direct effect on moss. (Lime does not kill moss). The effect on moss is indirect in that moss is less likely to grow. Higher pH is better for turf grass growth and increases nutrient availability. Lime adds Calcium to the soil which is an essential nutrient for turf grass.
  • Core aeration helps to loosen compacted soils and ease water movement into the soil. This will promote deeper root growth of your lawn, and helps dry out the surface.
  • Irrigate established lawns deeply and infrequently. Proper irrigation practices promote deep lawn root growth while keeping the soil surface dryer for longer periods of time.
  • Allow for good air movement to help in drying the area out. Enclosed areas such as fenced back yards or narrow side yards usually do not get enough air movement to dry the surface of the lawn. This increased moisture can lead to greater moss growth. When possible, remove or minimize obstacles that reduce air flow.
  • Control thatch layer and mow frequently to prevent moisture buildup. Early spring (late March – April) is a good time to thatch.
  • Practive good turf grass management. This includes proper watering, fertilizing and mowing.

Chemical Control:

Iron (also know as: Fe, Ferrous Sulfate, Iron Sulfate) is used to kill moss in lawns. Iron can be applied as a stand alone product, such as in Moss Out© or as a component of a fertilizer blend such as our Pro Spring 12-2-8 with 12% Fe. Apply when the turf is dry, then water the product in. The iron will cause the moss to turn black as it dies. The key to effective control with iron is thorough coverage of moss foliage. Severe moss problems may require a repeat application. In this instance, it would be best to use the Moss Out (or equivalent) product for one of the applications so as to not over-fertilize your lawn. It is important to rake out the dead moss. After the moss has been removed, the grass has a better chance to fill in. For severe moss problems that leave a lot of bare areas, it is a good idea to overseed the lawn. Country Green has several seed mixes to choose from.

** NOTE: Iron products will stain concrete, stone, driveways etc. Use care when applying. It is best to apply these products when it is dry, then sweep or blow any product off concrete before watering in.

Also, there are products on the market for killing moss on walkways and roofs. These often contain Zinc (Zn) or Copper (Cu). Do not use these products on your lawn. They are not labeled for use on lawns and the high concentration of Zn or Cu can harm your lawn.

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