I know that with all the COVID-19 situation going on and with the holiday season upon us and so many other things going on right now, moss is probably the last thing on most folks’ minds. However, as I think back it is amazing how many calls I get during the year about moss that is seemingly taking over my lawn or turfgrass area. It is a very common misconception of most folks who think the moss is killing out the grass; however, this is not true. Moss is very frequently found in areas of thin weak turfgrass. The very fact that moss is growing in an area of your lawn indicates that the environmental conditions in your lawn are not favorable for the growth of dense healthy turfgrass. In other words, moss will readily grow where your grass is not doing very well.
Many things can cause poor grass performance. The first thing you need to know is what kind of turfgrass is growing in your lawn. By far the most common reason for thinning turf (and the appearance of moss in its place) is very simply actually. That reason is the amount of sunlight verses shade that a given turfgrass area receives. Different types of turfgrasses have different light requirements ( although all of our common turfgrasses do better in full sun verses shady areas). The very same location may provide too much direct sunlight for one type and not enough direct sunlight for other grasses. Poor drainage, poor soil permeability, inadequate fertility (or too much fertilizer in some cases) as well as soil pH can all contribute to the thinning and weakening of your turfgrass and ultimately to the growth of large moss covered areas in your lawn.
Mosses are small, green, primitive plants that have reduced leaves and a mass of fine, thread-like stems. They produce a dense mat that covers the ground in areas where turfgrasses are not growing well, but the are not parasitic to the grass like many people believe. Although many species of moss can grow in lawns, they are all favored by the same or similar growing conditions. Some factors that favor moss growth include humidity, shady locations, infertile or compacted soils, poorly drained soils, or sometimes even areas with excess thatch.
Control of moss DOES NOT involve the use of herbicides. Contact herbicides will at best only temporarily “brown out” the moss at best. The only permanent control of moss is to correct the conditions that is causing the turfgrass to thin out. Here are a few suggestions for getting your turfgrass to grow better and thereby reducing the occurrence of moss in your yard.
Soil test the problem area as well as the rest of the yard. Separate soil samples should be collected from healthy turf and problem areas. Apply the fertilizer and lime as recommended by the soil test report you will get.
In moist places where there is poor drainage, contour or trench the area to move water away. In localized areas, adding soil or sand will slightly change the elevation and allow for drying. In larger areas that retain water, installation of French drains or tile drains may be necessary.
Trim the lower branches of shade trees to improve light penetration the soil’s surface and to improve air circulation. In partial shaded areas turf fescue may be a better choice than bermuda, zoysia, or centipede because of their relative lack of shade tolerance. Where there is heavy shade, it may be necessary to remove trees to maintain a dense healthy grass, or abandon the grass idea and convert the area to a “natural area” with very shade tolerant ground covers or other shade tolerant plants (which I personally think will save you time and money in the long run).
Cultivate or aerify the compacted soil areas to eliminate the compacted conditions that restrict root growth of turfgrasses. Any process that loosens the top two to four inches of soil will help improve the movement of water and nutrients in compacted areas. Cultivation or aerification also helps break up the dense mat of moss and will be necessary before re-seeding the area.
Chemical control is only a short term alternative to your moss problem. What that means is that if you only use a chemical and do not fix the underlying problem the moss will return.
Nonselective herbicides such as Roundup or other glyphosate products will kill moss as well as the desirable turfgrass. Re-seeding or re-sodding will be necessary in treated areas. Again, if you do not fix the underlying light, drainage, pH, or fertility problem the moss will definitely return.
The product copper sulfate is commonly used for algae control will also “brown out” moss. Apply three to five ounces of copper sulfate in three gallons of water per 1,000 square feet of turf area. The moss will brown out temporarily but will probably return.
The bottom line of the moss control story is to remember that the moss is there only because your lawn isn’t growing properly. You MUST find out the reason why your particular grass whatever type that may be isn’t growing well and correct that problem. Then and only then will you gain permanent control over moss related problems in your lawn.