University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Moss Problems in Lawns
Have Various Causes

March 16, 2000

Moss growing in lawn areas is a common problem that can have several causes. Keep in mind, however, moss is not likely to invade or crowd out vigorous grasses. Instead, moss develops as lawns thin due to poor site or management factors.

While we usually think just of shade, there are several problems that may allow moss to develop in a lawn. These include low soil fertility, poor soil drainage, compacted soils, excessive shade, poor air circulation, and high humidity. Often the site may have a combination of these conditions.

Poor lawn care practices are another source of moss problems. General neglect, irregular mowing, lack of fertilizer, and overwatering are common problems leading to poor turf growth that may in turn lead to moss problems.

What can be done about the moss? Moss can be eliminated, at least temporarily, by hand raking when it first appears. Ferrous ammonium sulfate or ferric sulfate (iron sulfate) can also be used to control moss. The moss will temporarily burn away, but tends to return fairly quickly unless the site conditions and/or lawn care program is altered.

It's best to focus on the cultural options for a more permanent answer to moss problems in lawns. Evaluate the site and make all necessary corrections to favor lawn growth. For example, prune trees to allow more light to reach the lawn and remove excess vegetation to improve air circulation over the site. Reduce soil compaction using cultivation practices such as core aerification.

Make adjustments to lawn care practices. For example, fertilize according to the type of grass growing on site and type of site. Lawns in full sun require more fertilizer than those in shade. Avoid excessive watering and mowing too short. Mow between two and three inches, preferably at the high end of the range for summer.

Finally, make sure the proper grass is growing for the site conditions present. Kentucky bluegrass is ideal for full-sun areas but does not typically do well in shade, thus tends to thin out and allow moss to invade. Fine fescue, such as red fescue, is a better option for shade. If fine fescue declines, consider a shade tolerant groundcover.


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