Mosses are green plants that have fine, branched, threadlike stems with tiny leaves and reproduce by wind-blown spores. They form a thick green mat at the surface of the soil and do not kill the grass as most believe but rather fill in the spaces in the lawn where grass is not growing.
The key to controlling moss is improving growing conditions to encourage a thick stand of healthy turf grass. The conditions that are favored by moss are excessive shade, poor drainage, acidic soil, compacted soil, low soil fertility, excessive irrigation, improper mowing or a combination of these factors that add up to thin or weak turf.
There are several chemical options from which to choose to kill the moss. Scotts and Ortho both produce a moss killer and another option is to use copper sulfate at the rate of 5 ounces in 4 gallons of water sprayed over 1000 square feet. After the moss has been killed and if you are going to reseed, it will be necessary to apply 5 to 10 pounds of ground limestone to inactivate the copper sulfate prior to reseeding as the copper sulfate may be toxic to grass seedlings. These materials kill the moss because they act as desiccants. They should be applied over the moss infested area during winter through early spring when moss is actively growing and temperatures are cool. Read and follow all package directions. Once the moss is dead, remove it by raking. You may like the non-chemical approach and try to rake as much moss from the grass as possible.
Unless you treat the underlying conditions to favor grass growth, any solution you try to get rid of the moss will only be temporary. One of the first things I recommend is having the soil tested. Mosses prefer acidic soil while grass prefers a pH of 5.8 to 6.5. Check with your local Extension Service or local grain elevators as they offer soil testing instructions, bags and an address to send your sample to. Once you have the test results your lawn can be treated accordingly.
Plant a more shade tolerant grass and mow grasses in a shady area at the top of their recommended mowing height range to encourage deep rooting and provide maximum leaf surface for the manufacture of food.
Consider pruning some low lying limbs from surrounding trees and bushes for better air circulation and to allow for more sunshine to reach the grass.
Compacted soil can be corrected with core aeration. This process involves physically removing cores of soil from the lawn and helps to improve the growing conditions for grass.
As always, Happy Gardening!
More information about gardening and related subjects can be found online. The Purdue Extension Service can be reached at 499-6334 in LaGrange Co., 636-2111 in Noble Co., 925-2562 in DeKalb Co. and 668-1000 in Steuben Co.
Karen Weiland, Purdue Master Gardener, Purdue Extension, LaGrange County
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