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Controlling moss and algae in turf
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As turf grass areas occasionally begin to thin out, moss and algae begin to form because conditions for growing dense, healthy turf have declined.

Mosses are branched, threadlike green plants that form a tangled, thick mat over the soil. Algae are threadlike green plants which form a dense, green scum over the soil surface.

Neither moss or algae are thought to be parasitic, but both are spread by windblown spores. Both can form crusts on the soil surface, reducing air and water movement into the soil.

Factors favoring their development include wet and humid conditions and compacted soils of thin turf. Moss is more common in shady areas with infertile, acidic soils and excessive thatch. Algae prefers full sun conditions and fertile soils.

Cultural practices favoring growth of turf grasses will reduce the competition from moss and algae. These practices include the following:

Maintain good soil fertility and pH

Have the soil tested to determine proper lime and fertilizer needs. For most turf grasses the pH should be about 6.0 to 6.5.

Improve drainage

Soils that stay moist because of poor drainage should be contoured so water will drain. In some cases, tile drainage may be necessary to correct wet conditions.

Increase light penetration and air circulation

Pruning tree limbs below 10 feet and selected limbs in the crown will improve light penetration and air movement. Also removing some of the least desirable trees and thinning and/or removing shrubs will help. Areas surrounded by buildings and vegetation with limbs close to the ground may require considerable work to provide adequate air circulation and light penetration.

Use a shade-tolerant grass

Use a turf type of tall fescue. However, if direct sunlight does not reach the ground for at least six hours, an ornamental ground cover may be better suited.

Cultivate compacted soils

Aerification with a machine that removes plugs of soil will help reduce compaction. Core aerifiers may be rented, purchased or contracted through lawn service companies. Drainage in fine-textured soils can be improved by cultivation and adding large amounts of organic matter.

Irrigate deeply and infrequently

Avoid light-frequent irrigations. Wait for signs of moisture stress such as the development of a bluish-gray, dull color before irrigating. Irrigate to wet the soil to at least six inches. Most healthy turf grasses need about 1 inch of water per week during active growth. If puddling occurs, stop irrigating and wait two to three hours for the water to soak into the soil before watering again.


Generally, turf may be renovated if turf cover is less than 50 percent, then re-establishment will be needed.

Soil test, till and fertilize based on soil test results when you are renovating your lawn. Overseeding may be an option to thicken up the lawn if it is less than ideal, but not so bad you can justify a complete renovation.

The bottom line to remember is that moss and algae grow because nothing else will. Simply adding grass seed to an area will not work in the long term. You have to figure out what is wrong with the growing conditions and fix them so the grass can out compete the moss and algae.”

Michael Wheeler is county extension coordinator for the UGA Cooperative Extension office in Hall County. You can contact him at 770-535-8293, His column appears weekly and on

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