2009-06-03 / Fields & Yields

Home & Garden Tips

Moss Management
By Roosevelt McWilliams County Extension Agent

You may have noticed when cutting your grass that what was once your nice, thick, green lawn has turned into a not-sonice, green something else. What is this stuff that is taking over the lawn? Can it be stopped from spreading over your entire yard? Most likely the problem is moss, although in some cases it may be algae.

Moss and algae are simply plants that are looking for a home and if the right conditions are provided, they can quickly take up residence and do quite well. This is the way nature intended it, so let's see what created the conditions for these two turf pests to occur in the first place. Mosses are small plants which produce a mass of fine stems that can survive under very shady conditions. Moss will take over and grow where the shade is so dense during the summer that not enough light is present to support growth of the turfgrass. Moss thrives during periods of high humidity and in water-logged soils.

Algae is a very simple plant that has no vascular system. It usually forms a dense green mat or scum over the soil surface, although reddish or brownish forms may also occur in some situations. Algae need plenty of water and lots of sunshine for growth. When the soil dries, algae form a black crust which becomes hard and relatively water resistant.

The good thing to know is that these plants are not parasitic and therefore do not kill grass like diseases do. They are a good indicator that your lawn needs help. One factor that is common with both moss and algae is that the growing conditions for lawn grasses are poor. The principal problems are usually hard, com- pacted, clay soils that restrict root development. Soils with high clay content, like the soils we have are easily compacted from foot traffic and the settling of clay particles over time as water works through the soil profile.

The best solution to this problem is the use of a soil aerator that removes plugs of soil from the ground, thus enhancing soil drainage. If the affected area has very little grass, it is better to start over. You should till the soil to depth of 6 inches to break up the restrictive layer. This will also facilitate incorporation of lime and fertilizer into the soil. A soil test should be taken to determine plant nutrient needs. Soils with low fertility and low pH (acidic) lead to poor growing conditions for grass and make it easier for algae and moss to become established.

Improving the drainage with the incorporation of organic matter is also beneficial. Low areas that do not drain well should be contoured. In some cases, the use of drain tiles can help remove excess water and improve growing conditions for turfgrasses. Sometimes we may create water problems by watering too much. Irrigation systems should be adjusted to match the soil conditions and plant needs.

Moss can become very thick under heavy shade conditions. Thinning trees or pruning limbs to improve light conditions and increase air circulation is helpful.

Many people ask me if there are chemicals available to eliminate moss. Although some chemicals are effective, they are only temporary and the problem will return in time. Copper sulfate can be applied at the rate according to label directions. The only sure method of eliminating moss and algae is to remove them by hand raking.

Remember, getting rid of moss and algae is the easy part. When these problems occur it means that something needs to be done too.

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