Home / Gardening in the South / Slime Molds, Nostoc Appear in Yards after Heavy Rains
Slime Molds, Nostoc Appear in Yards after Heavy Rains
Nostoc growing on the lawn of St. Michael's Catholic Church in Auburn, Alabama.

Slime Molds, Nostoc Appear in Yards after Heavy Rains

 AUBURN, Ala.—Many Alabama homeowners felt the effects of torrential downpours in the garden and in their yards.

Dr. Dave Han, an Alabama Extension turfgrass management specialist, said homeowners may see a plethora of strange-looking organisms popping up in the yard.

“Besides the usual mushrooms, moss and algae, two strange-looking things are popping up: slime molds and Nostoc,” Han said.

Slime Molds

“Slime molds are really cool critters that live in soil and thatch, feeding on organic matter,” he said. “When it rains, they will ooze up onto the foliage of the lawn in order to reproduce. They sit on the surface of the leaves and produce spores, which will dry up and disperse.”

slime molds

Slime molds on the fields at the Auburn City Soccer Complex. Photo by Dr. Han.

Slime molds can grow in many different colors. Yellow and purple/black types occur are most commonly on turfgrass.

Han said yellow ones may be mistaken for dog vomit, while the dark ones could be mistaken for oil or soot. Harmless to turf, remove them by hosing down the molds, or when they dry out, by brushing or mowing the grass.

Additionally, Han said homeowners should not worry because slime molds are not harmful to people or pets.


The other strange-looking organism popping up in yards is Nostoc, which is a genus of cyanobacteria. Cyanobacteria is a photosynthetic bacteria also known as blue-green algae, but is of no relation to true algae. Nostocs produce a greenish or blackish-green gelatinous matrix and appear most often on turf.  Some people say it resembles pieces of really ugly gelatin on the turf.

Han said if one ventures to pick them up, they would feel like gelatin, too. These are slippery to walk on when wet, but dry out to a dark crust.

Nostoc growing on the lawn of St. Michael’s Catholic Church in Auburn, Alabama.

“Like slime molds, Nostoc is not a parasite of grass, but if enough of it covers the turf it can cause shade issues,” Han, who is also an associate professor in the Crop, Soil and Environmental Sciences Department at Auburn University, said. “Usually it appears in places where the turf is already thin, taking advantage of the lack of competition.”

Han said Nostoc can fix nitrogen. This means it can grow in areas of low fertility— and it some cultures it is eaten as a food.

Nostoc control methods include drying out areas where it grows and thrives.

“It is moderately sensitive to copper-based algacides and very sensitive to herbicides with pelargonic acid,” he said. “Because this is a non-selective product, only use this herbicide where burning the turf can be tolerated.”

With more rain expected, look for more slime molds and Nostoc.

More Information

For more information, visit www.aces.edu. Contact your local Extension office for assistance at home. More information on slime molds can be found here.

About Katie Nichols

One comment

  1. Thanks for your site. I’m always looking for content you