UNIVERSITY PARK, Pa. -- Moss is one of the most persistent and annoying weeds that occurs in home lawns, but you can control it, says a turfgrass scientist in Penn State's College of Agricultural Sciences.

"To control moss, you have to consider the reasons why it began to grow in your lawn," says Peter Landschoot, associate professor of turfgrass science. Moss usually thrives under conditions that aren�t conducive to good turf growth, such as poor soil fertility, acid soil, heavy shade, excessive moisture or shallow, rocky soils."

"Moss is an opportunistic plant that grows in bare soil or where grass is weak and thin," says Landschoot. "Once moss has invaded the lawn, grass won't spread into those areas."

Attempts to get rid of moss are rarely effective unless a dense, actively growing turf can take its place, he says.

The first step in controlling moss is to test the soil for nutrient content and pH. Soil test kits are available from your county cooperative extension office for a nominal fee.

"If the soil is deficient in nutrients or needs to be limed, the soil test report will indicate how much fertilizer and lime to apply and when to apply them," says Landschoot. "Over time, improved soil conditions will help your grass compete with the moss."

If shade or moisture limit good turf growth, steps can be taken to correct the situation. "For example, remove some trees or tree branches to increase sunlight and air circulation, or plant grasses that are adapted to shaded or moist areas," he says.

"Fine fescues adapt best to shaded, well-drained soils, while rough bluegrass is better adapted to shaded, moist soils," he says. "But neither of these species survives in extremely heavy shade or soils that are saturated for long periods.

"Attempt to eliminate moss with chemicals only after the limiting factors for good turf growth have been corrected," says Landschoot. "Unfortunately, there are only a few chemicals available. These products contain salts that will dehydrate or 'burn' the moss. But they also can burn desirable turfgrasses if used improperly, so be sure to follow the directions on the label." Remember, it took a long time for moss to take over your lawn, it will also take a long time to control it.

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EDITORS: To contact Peter Landschoot, please call 814-863-2719.

Contacts: John Wall John_Wall@agcs.cas.psu.edu 814-863-2719 814-865-1068 fax