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Mosses and algae are primitive plants. They do not kill lawns directly. Instead, they take advantage of ideal conditions for their growth and then take over an area. This is related to factors such as too much shade, soil compaction, poor drainage, poor air circulation and improper pH. Mosses and algae are objectionable because they interfere with the carpet-like appearance and texture of the lawn.  Mosses produce a fibrous, matted type of growth on the soil surface.  Algae interfere more with the growing conditions for the lawn than the appearance. They form a bright green, slimy layer over the soil.  When this layer dries out it becomes a black impervious crust.

Moss and algae do not appear in vigorously growing lawns. All of the conditions that favor the growth of moss and algae will hamper the growth of grass.  Their presence invariably points out that there are environmental problems that need attention. In short, if there is a moss or algae problem, the key to establishing a nice lawn isn’t to kill or remove the moss or algae but to change the conditions to favor turfgrass.

Conditions That Promote Moss Growth

  • The soil is poorly aerated (i.e. compacted)
  • There is excessive moisture
  • The soil is too acidic and fertility is low
  • There is shade

Conditions That Promote Algae Growth

  • There is a wet, saturated soil surface (standing water)
  • Fertility is high and mowing heights are low
  • There is full sunlight

Improving Conditions to Favor Turfgrass Growth

  • Maintain good soil fertility to help improve turfgrass health and competitive ability.  Maintain good nitrogen and potassium in your program.
  • Improve drainage.
  • Provide selective pruning and/or remove dense shade to improve light.   
  • Plant shade-tolerant turfgrass varieties, if shade is a factor.
  • Reduce soil compaction with annual core aeration.
  • Improve air circulation by removing low-growing tree branches.
  • Test soil and correct soil pH if imbalanced.  Moss favors acidic soil.
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