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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

With early greening grass comes moss

It was nice to see the grass green up three weeks early this year. It took away the drabness from the winter landscape at just the right time. Unfortunately something else greened up rather early this year because of the warm winter: moss.

Moss is one of the Earth’s oldest plants. It has been around for millions of years and has survived and thrived in that time. It is so old that it reproduces by spores carried on the wind rather than by seed. It also does not have any vascular system to move water and nutrients through the plant. Instead it absorbs water and nutrients through its leaves and uses direct photosynthesis to create food through the harvest of carbon dioxide and sunlight. This simple existence means that moss can adapt to a wide range of places where other plants, including your lawn, don’t do very well.

Most often, moss thrives in areas where the lawn has been worn thin and the soil compacted by overuse, is under drought stress, has poor drainage, is too shady, has been improperly mowed and fertilized, has a poorly prepared lawn seed bed planted with the wrong type of lawn grass and acidic soil conditions. Usually it is a combination of several of these factors.

Correcting the issues that allowed the moss to move in will take time, patience and a fair amount of work. Because these conditions revolve around issues of fertility, soil acidity and growing conditions, start with a soil test to determine the levels of nitrogen, phosphorus, potassium, organic matter and pH in your soil. Knowing these levels gives you a starting point for correcting the issues and help prioritizing your efforts. The Spokane Conservation District can run this test for $30. The test will offer recommendations on how to alter your pH and how much fertilizer to apply. Information on taking the soil sample and submitting it are available at www.sccd.org.

With the results of your soil test in hand, you can plan your remediation program. Thin out dense trees and shrubs that shade the area to let in more light. With improved light, the grass will grow better. Thinning some of the shrubbery might also remove foliage that is blocking sprinkler heads. Mow the lawn no shorter than two to three inches so the grass blades have enough leaf area to generate the needed nutrients. If the soil has been compacted, aerate the area with a core aerator each fall and spring for a couple of years to allow water and nutrients to get deep into the soil. Then lay down a two-inch layer of compost and then overseed the area with a more shade tolerant variety of lawn seed. If your soil test says your lawn has a low pH, you will need to apply the recommended amount of lime called for. Lawns in this area do best with a pH of about 6 to 7. Lime in several forms is available at local garden centers.

Pat Munts is the co-author of Northwest Gardener’s Handbook with Susan Mulvihill. Munts can be reached at pat@ inlandnwgardening.com.