Many homeowners feel frustrated when lawn moss invades their yard. It is in fact one of the most common lawn problems reported to county extension services. Don Janssen, extension educator, recommends that homeowners determine why moss is there in the first place; moss usually becomes established because of soil compaction, too much shade, poor drainage, or low soil fertility. Take control of lawn moss by understanding and correcting the cultural needs of your lawn.
Pull out large areas of moss when it is actively growing in the spring with a flail-type dethatcher.
Thin branches on shade trees selectively to improve the light quality and airflow beneath the canopy. Grass needs six to eight hours of filtered light or three to four hours of direct sunlight for healthy growth. Moss will return unless actively growing grass or groundcover takes its place, so if you can't provide more sunshine replace the lawn moss with a shade variety of grass.
Reduce soil compaction by core aerating your lawn annually. Core aerators are machines about the size of a garden tiller that punch out a cork-sized hole in the lawn every few inches, tossing the plugs onto the lawn to decompose. Lawn growth is stimulated with improved airflow, water trickling to grass roots, and new seed gaining soil contact in the holes and on surface plugs. Rent a machine through a local rental store or hire a lawn service for assistance.
Eliminate poor drainage and low spots, regrading your lawn if necessary. Wet spots after heavy rain are unavoidable, but standing water days after a storm drowns the grass and sets up the perfect conditions for lawn moss. Add soil and seed to build up low spots after addressing the soil compaction.
Overseed thin areas. Moss does not invade thick, lush lawns. Set your mowing height at 2 1/2 to 3 1/2-inches for healthy lawn growth.
Test your soil. A soil test can determine if you need to correct the pH of your lawn; a neutral pH of 6.5 to 7 is ideal for healthy lawns. Add a soil amendment such as lime to adjust the pH if needed.