You may have noticed greenish/brown jelly like blobs appearing in your drive way or lawn. That is called Nostoc. It is a type of bacteria that gets its energy from photosynthesis like plants do. Following a period of rain, it may appear suddenly in lawns, pastures, paved surfaces, roofs or stones. Nostoc has many colorful names including witches’ butter, mare’s eggs and meadow ears, among others. In fact, one of the earliest names for it was star jelly, based on the belief that it was a remnant of shooting stars fallen to earth.
It can be hazardous on paved surfaces as it is very slippery when wet. From its gelatinous, green state, it dries to a black crust that comes back to life when there is sufficient rain. When found in lawns, it is generally on a site where the grass is growing poorly due to severe compaction, over-watering or both. It has not caused the lawn’s decline; it has simply colonized an area where it has favorable conditions to grow. Poor drainage, compacted soils and fertilizers containing phosphorus create a favorable environment for colonies of Nostoc.
To discourage its growth, improve drainage and eliminate phosphorus fertilizers. Products that contain potassium salts of fatty acids may be used to kill it in lawns. Core aerating the lawn to reduce compaction may help, but tilling the soil will merely break it into more pieces and encourage its spread. For paved surfaces and small patches in lawns, shoveling it up and discarding it in a landfill may be an option. Another option would be to choose a lawn chemical designed to control algea and moss.
The good news is that although they are a bit alarming looking, they do not cause any harm. Although we may not appreciate it growing in our lawns or on our pavement, Nostoc possesses many redeeming properties. Several Nostoc species have been used as both a food and medicine for centuries, and have more recently been evaluated for their pharmaceutical properties, including antibacterial metabolites, cholesterol regulation and control of certain cancers.
Submitted by Amanda Sears, Agent for Horticulture, Madison County Cooperative Extension Service