Controlling Moss in Lawns

Moss is red flag for poor lawn conditions

Bill Sevier: Ask a Master Gardener   

Saturday, April 9, 2016  

Q: In a shady part of my lawn, there is moss growing in some bare spots. Is there something I can spray to get rid of it? Alan, Tulsa

A: There are sprays to kill moss, however, to not address the underlying problem is the wrong approach.

Moss, like an invasion of undesirable weeds, is usually a red flag that something is wrong with your turfgrass growing conditions. Situations favoring moss growth are too much shade, poor fertility, excessive moisture, soil compaction and overly acidic soil. The best solution is to identify and correct the problems; if not, moss will only return.

To correct deficiencies, start off with a soil test. This will measure soil pH (acidity) and the nutrients nitrogen, phosphorus and potassium.

The pH needed for most lawn grasses is slightly acidic — between 6 and 7. Most turfgrass in Oklahoma will grow but perform less well in more acidic soils. Moss prefers just the opposite, growing better in more acidic soils. To correct an overly low pH, add dolomite lime. This adds alkali and raises the pH to more favorable levels. Instructions about using lime may be found in OSU fact sheet 6007, “Improving Garden Soil Fertility,” at tulsamastergardeners.org.

Many mossy lawn patches are compacted, often related to foot or vehicular traffic. To reduce compaction, till 3 to 4 inches of organic compost into the soil. This will not only improve drainage and air movement, but will also add fertility. Do not use peat moss as your organic compost; peat moss is too acidic and may make the situation worse.

The soil test will indicate which nutrients may be needed. Add only those suggested by the test results. Do not add nutrients such as phosphorus unless proven to be deficient. Adding more to soils with pre-existing high levels will not only harm plants, but also can result in pollution.

Areas that are too shady may be difficult to deal with unless trees can be pruned to allow more light. Likewise, overly wet soils will need some attention to drainage depending on the situation.

Several commercial products are labeled for moss control. These contain either a type of soap, bleach or various mineral salts of copper. They all seem to be somewhat effective. However, many of these preparations may also damage other plants, so the label must be read and followed carefully.

After eliminating moss, shady areas can be planted with tall fescue turf grass, or if too shady for fescue, plant a shade-tolerant ground cover. OSU has an excellent fact sheet, “Managing Turfgrass in the Shade in Oklahoma,” available online.

Be aware that growing moss is not considered undesirable by everyone. Some people go to great extremes creating “moss gardens” as a place of peace and serenity. Several books have been written about how to create these gardens. This fact demonstrates clearly the adage that “beauty is in the eye of the beholder.”

For more information or to ask a question about gardening, contact the Master Gardeners at 918-746-3701 from 9 a.m.-4 p.m.

Garden tips

§  March is the second best time of the year to seed cool-season turfgrasses — tall fescue and Kentucky bluegrass; however, fall is far and away the best time to plant them.

§  Prune roses as needed now and begin a regular spray program on varieties susceptible to black spot disease.

§  Early to mid-April is the time to plant most warm-season vegetables such as Lima and green beans, cucumber, pumpkin, summer squash, tomatoes, eggplant, pepper and okra. Complete listings for when to plant cold-season and warm-season vegetables may be found online. It is titled “Oklahoma Garden Planning Guide,” #6004 and may also be found on the Master Gardener website.