I like to have a nice-looking lawn and there is a section of my lawn in the back corner under some shade trees that has a lot of moss growing in it. How can I get rid of the moss?
— Jerry Shapiro, Glenview
I often see moss growing in lawns around the North Shore, so this problem isn’t unique to you. The moss growing in your lawn is a sign that your grass is weak and has thinned for some reason in that area. Moss likes sites that have poor drainage, that are shady and damp with acidic soil. Most garden soils in the North Shore are more alkaline, though, so I’m guessing the key conditions that encourage moss in your lawn are moisture and shade.
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Of course, there are plenty of other factors that might be contributing to the problem: excessive shade, compacted soil, poorly drained soil, low soil fertility, and poor air circulation are all possible issues. Mowing too low can also encourage moss.
The best way to manage this problem is to modify that area of your lawn to favor grass and discourage moss. Prune the shade trees to increase sunlight to the lawn — but avoid over-pruning, since I feel the trees have more value to your garden than the lawn! Reduce the amount and frequency of watering in this area, too, to maintain drier soil. In general, it’s best to water lawns more deeply and less frequently; err on the side of keeping the moss-infested area dry. Increasing the amount of sun to the lawn and keeping it drier will be the two most effective things you can do.
You can also core-aerate your lawn and overseed it with a high-quality grass seed mix for shade. Core aeration will help reduce soil compaction, and grasses adapted to shade will do better in this spot. I mow my lawn at 3 to 3½ inches to promote strong turf that’s more stress-resistant, which helps it compete with weeds. Of course, if changing your lawn-management techniques doesn’t eliminate the moss, you might ultimately find yourself accepting it.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at [email protected]. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.