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Spring Moss Control in Northwest Lawns

by Gabby Hyman, All About Lawns Columnist

The Pacific Northwest is a breeding ground for moss. Despite the drought of 2001, the west side of the Cascade Mountains continues to receive heavy winter rains and, with them, ideal moss-growing conditions. According to Washington State University, February is an ideal time to battle moss growth in your lawn.

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Moss may seem inevitable in the Northwest, but it really can't compete for air, water, and nutrients in a healthy lawn. That's why you'll find it growing in bare spots of your lawn where the grass has been stress damaged or depleted of sunshine from overhanging tree branches. It also occurs where the lawn is overly compacted, too acidic, or has poor overall drainage.

Corrective Measures to Fight Moss

If you already have rampant moss growth, February is a good time to apply a moss killer. Brands vary, but the most effective contain iron (ferrous ammonium sulfate, ferrous sulfate, or ferric sulfate) and potassium salt. Follow directions carefully, as the iron can stain sidewalks and driveways. Recommended ranges are from .5 - 1.5 pounds of iron for each 1,000 feet of lawn.

Next, aerate your lawn to prevent too much compaction. Aeration increases drainage, eliminating pools where moss can cultivate and thrive. Have you dethatched your lawn in the last few years? You may have to do this in addition to aeration because too much dead grass residue prevents drainage.

Checking soil pH is important. In the Pacific Northwest, lawns love a soil pH between 6.0 and 7.0. If your soil is too acidic, apply lime. It's wise to consult your local university extension or lawn care service to determine the right amount of lime for your local soils.

When you're done treating for moss, you should over-seed the bare areas to eliminate future moss habitat. Ryegrass (or fescue) is a solid choice.

About the Author
Gabby Hyman has created online strategies and written content for Fortune 500 companies including eToys,, Siebel Systems, Microsoft Encarta, Avaya, and Nissan UK.

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