Della King Contributing columnist
September 30, 2013
Question: What is the dark mold looking substance in my lawn?
Answer: Have you ever seen an unusual mold or slime growing on your mulch or lawn? The description of this odd curiosity varies among people. Some say it looks like a dark mold growing on the grass. Others say, for lack of a better description, that it looks like “dog vomit.” No matter what your description is, it is usually referring to what is called slime mold.
Slime mold is a fungus that feeds on decaying organic matter. Slime mold may look alarming but it is not a plant disease that harms plants. Slime mold grows on the outside of plants or close to the ground usually on mulch. This mold normally shows up in moist, shady places but can show up in other areas. Moisture is what drives slime mold. Slime mold usually shows up quickly after a good rain shower. It also is common in areas that tend to dry slowly. There are factors that can encourage moisture, thus encouraging slime mold. Shady areas, thatch build-up in the lawn, low lying areas, or poor soil drainage can all be ideal areas for slime mold.
Slime mold can show up in a couple of different forms. This mold produces spores that are wind-borne and can remain viable for years allowing the mold to survive when conditions are unfavorable and show up when favorable conditions are present. When moisture is present, the spores release additional spores that move in a slimy substance that covers the surface of mulch or grass. As the slime spreads, it produces dark-colored spores that can be visually seen on leaf blades. Because the slime mold occurs in different forms, that is why it is often described differently. The color of the slime form can be cream, brown, yellow, orange, or dark red. The mold form can appear as patches of gray, dark blue, or white mold on grass leaf blades.
Even though slime mold can be alarming, it does not pose any threat to the lawn or plants. The mold will disappear about as quickly as it appeared. Once the area dries and loses moisture, the mold will disappear until moisture returns. If the slime mold is occurring in a location where it will be unsightly, you can remove the slime mold with a rake, broom, or by mowing. You can remove slime mold by spraying with water, just be sure to spray with water only with the onset of dry weather to prevent encouraging additional moisture for the slime mold to continue growing.
Slime mold is one of those landscape curiosities that causes concern but is not something to worry about. Slime mold will not cause any problems in the lawn or landscape and will disappear when dry weather returns.
Reminder: If you would like to learn more about Horticultural related topics, then join the “Sampson County Friends of Horticulture”. This program offers monthly “How To” Horticultural Seminars. Please call 910-592-7161 for more information. Please call the Sampson County Cooperative Extension Center at 910-592-7161 with your horticultural questions and to register for any upcoming events. Be sure to check out the Ask An Expert Widget at sampson.ces.ncsu.edu for any questions you may have.
(Editor’s note: Della King is the Agriculture Extension Agent, Home Horticulture for the N.C. Cooperative Extension Service in Sampson County.)