I have a lot of fairly thick, short moss growing on my lawn. The grass seems to be growing through it and looks healthy, but I still have a carpet of moss. I try raking it, but it's relentless and continues to grow. What can I do about this?
Moss loves acid, compacted soil. Ph is merely a measure of H+ ions in the soil. Rain will leach other cations from the soil, such as Ca++, Mg++, and K+ in about that order and with Ca++ being mostly leached. When this happens, H+ takes their places. This produces an acid soil. Also, the presence of Ca++ in abundance in soil will cause the clay particles to flocculate, or draw close together. Having the clay particles close together actually does the opposite of what you'd guess... it makes the soil looser and resistant to compaction.
So the solution to a moss problem is extremely easy. Just add calcium. The Ca++ will displace H+ ions and reduce acidity. The Ca++ will flocculate the soil and reduce compaction. Grass will again want to grow in the area.
Aeration does very little. The soil will fill in the little holes and go right back to its compacted nature since the cause of the compaction has not been addressed, namely, lack of Ca++.
Moss cannot compete with grass under ideal conditions for grass. You could cultivate a moss garden. It never needs mowing!
To improve conditions for grass you can do some or all of these:
- more light: can you cut back any trees or shrubs to let more light in?
- reduce compaction due to foot traffic or absence of organic matter
- add a hard path where people walk
- sow more grass seed and then top dress twice to 1/4" to 1/2" yearly with weed free compost or topsoil
- aerate the soil: the best method is to physically remove plugs of soil (takes more work than using a hard rake)
- drainage: does water sit in puddles after a rain? some regrading to let water flow off the turf might help
- use a hard rake to physically remove the moss before seeding and top dressing