How to help a lawn that's being overrun
My home faces north and has a front yard dotted with a number of trees, but the lawn is gradually being overrun by moss. What is the best way to eliminate this problem?
— Allen, Annapolis, MD
Roger Cook replies: Moss loves shady, moist conditions, so exposing it to sun is one of the most effective ways to get rid of it. But short of taking down some trees (or moving the house), the best thing you can do is give up on the grass and introduce some shade-loving groundcovers, such as ivy, pachysandra, ajuga, epimedium, or thymus. (For visual interest, you could also add some larger shade-loving plants, such as ferns, hostas, azaleas, or rhododendron.) Prepare the soil by Rototilling outside of the drip lines of the trees (you don't want to damage their roots). Then, till in a one-inch-thick layer of compost, cover it with a one-inch layer of sand, and till that in also. Now it's ready to plant. Once established, these plants require far less maintenance, water, and fertilizer than a lawn.
But if you simply must have a lawn, you could try planting shade-tolerant grasses such as perennial rye or fescue. Test your soil first—moss is an indicator of acid soil—then Rototill the area. To improve the quality of the soil, add loam and till it in, then add compost and till it in. Now add fertilizer and lime—your cooperative extension service can test the soil and prescribe how much of each ingredient is needed—and till again to mix the materials together. Finally, rake out the ground to its finish grade, and spread the seed.
You should prune surrounding trees as much as possible to let more sunlight in, and follow up with maintenance pruning every three to five years. Also, remember to test the soil annually and add more lime as needed. (When conditions stabilize, a soil test every two or three years will be sufficient.) If you let the soil become acidic again, the moss will reestablish itself.