Moss grows best in shady moist conditions and can be a symptom of poorly drained areas of the lawn. Moss may appear in places where mower blades have scalped the lawn and where there’s no grass to compete, the moss establishes itself and takes over.
Sometimes the problem is due to thatch, that nearly impenetrable mat of dead non-decomposed stems that prevents water from getting into the soil. For thatch, use a power rake, hand rake or a dethatching mower attachment set low enough to break through the thatch.
For both thatch and compacted soil, aerate the lawn with either an aerator, a pitchfork or spading fork to a depth of three to six inches. This will allow air circulation to the root level and will let water, nutrients and fertilizers to get into the soil rather than running off.
Too much shade
Moss is commonly seen where lawn conditions are shady and damp. Pruning trees, shrubs or overhead vegetation to open up the area to sunlight may help. If pruning isn’t an option, consider replacing the problem lawn with shade loving ground cover plants and decorative bark mulch. Shade grass, sometimes referred to as fescue grass, is also an option as it’s tougher, shade tolerant and usually grows well in cool conditions.
If the moss is in a low-lying area, create a drainage channel or raise the overall level of the yard by filling with topsoil and reseeding.
Ongoing lawn maintenance
Fertilizing the lawn
Some spring lawn fertilizers contain a moss killer, and specific moss control products are available under various brand names. Ferrous ammonium sulfate is usually added to fertilizer mixes and will turn the moss black, at that point it can be removed by raking it out; then reseed the bare spots. Fertilizers high in nitrogen tend to stimulate top growth but don’t provide all nutrients required for a healthy vigorous lawn – a calcium nitrate fertilizer might be used instead; it will also help deter the moss and sweeten the soil if it has become sour.
Watering the lawn
Watering thoroughly and deeply and only when the grass needs it will encourage roots to grow deeper where watering too frequently causes the grass roots to remain shallow and also encourages weeds to germinate.
Mowing the lawn
Mow with sharp blades; dull blades tear the grass rather than cut it. Most species of grass should be kept about three inches tall, keeping it this long helps prevent weed seeds from germinating in the lawn, keeps the soil from drying out too quickly and reduces the need to water frequently.
Photo credits: Microsoft clipart
Research credit: Dale Timmermans and thanks for getting rid of the moss hun!