Moss thrives in infertile soil and damp, shady conditions.
Thick, healthy turf needs plenty of sun and soil that’s rich in organic matter.
“What do you have that gets rid of moss? Moss is killing my lawn,” a customer asked me last week. Concerns about mossy patches in the home turf fall into the FAQ category, especially here in the rainy Northeast, and misconceptions abound.
The truth is, moss doesn’t actually kill lawns. In the natural world, moss is an opportunist, an early colonizer of terrain that other plants find inhospitable. It thrives in infertile and acidic soil, shade, and consistently damp conditions. Moss doesn’t mind compacted soil; it grows on rocks, after all.
Modern turf grasses, on the other hand, are descended from grass species that populate sunny meadows and prairies with deep, rich soils. These are old, organic-rich soils that have been fed for millennia by decaying plants, nitrogen-fixing clover and other legumes, and the dung of grazing animals. Beneficial soil fungi, called mycorrhizae, inhabit the soil and help the roots absorb nutrients. Windswept rains easily percolate down to the deep roots, then move on, leaving the foliage to dry quickly in the breeze.
Moss and grass have very different cultural needs, so my first question, when a customer complains about their mossy lawn, is, “tell me about the growing conditions in your yard.” Nearly every time, they say that their lawn is shady, they’ve never checked the soil pH or fertility, and that they either don’t fertilize at all or they use a chemical fertilizer or weed-and-feed product. Essentially, their home ground is ideal for growing moss and not grass.
The first step in eliminating the moss is to change the conditions that favor its growth over that of the grass. I always recommend starting with a professional soil test for pH and basic nutrients. The test results usually include specific soil additive recommendations, such as the amount of lime needed to raise the soil pH to a certain level. Adding organic matter, aerating the soil, and increasing the sunlight through selective pruning help promote good turf, too.
The next step is choosing the correct turfgrass mix for the area. Some grasses are better suited to partly shady conditions. The healthiest lawns also include a mix of grasses and nitrogen-fixing legumes, like clover. Legumes tend to have deep root systems that help to keep the soil looser and more easily penetrated by rain and oxygen.
The last step is maintenance. Using natural fertilizers that don’t harm the mycorrhizae and other soil organisms is key. Choosing the correct mowing height, keeping mower blades sharp, and watering deeply also promote healthy turf.
For more on establishing and maintaining a healthy lawn, read The Natural Lawn.