Slime Molds

Need to know: 

  • Slime molds feed on decaying organic matter. 
  • Appear most often after a warm summer rain. 
  • Usually last one to two weeks. 
  • Slime molds aren’t normally a problem, if needed can be removed by raking, sweeping, or mowing.  
Image of slime mold on turf grass
Slime mold on turfgrass

Overview of slime molds 

The presence of slime mold is more of a curiosity than a problem. Slime molds are primitive organisms that are considered fungi. They feed on decaying organic manner and other organisms in the thatch layer and soil.

Symptoms of slime molds

Slime molds often appear after a warm summer rain. At first a slimy growth, called the plasmodium, appears. This slimy growth dries into a powdery mass of spore-bearing structures that coat grass blades. Slime molds usually last one to two weeks and often are observed in the same spot year after year. Typically 4-6 inches patches of the fungus are formed. Although there are many species of slime mold on turf, Physarum cinereum seems to be the most common. Slight yellowing of turf can occur as the slime mold blocks grass underneath it from being able to do photosynthesis. The grass will almost always recover though if the slime mold is removed.

Signs of slime molds

Slime molds are often brightly colored and the fungal body can be seen coating patches of a lawn. When the masses are young, they are sticky but dry out as they age. 

Management of slime molds  

Control measures are not usually necessary. If desired, slime mold can be removed by raking, sweeping with a broom, or mowing.  However, it is possible that the slime mold will reappear under humid and warm conditions.

Image of slime mold on wood chips
Slime mold on wood chips 
Image of slime mold on a perennial
Slime mold on perennial


Last reviewed:
April 2022

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on September 1, 2016. The information contained within may not be the most current and accurate depending on when it is accessed.