Several times a year, inquiries come to the Pulaski County Extension office regarding some 'black stuff' or 'gooey growth' around a mailbox, in gravel drainage ditches, or in some thinning turf.

When wet, the growth is gooey and bubbly-looking. When dry, it's crusty and hard. But with the next rainfall or irrigation, the gooey stuff reappears. It can go through these wet/dry periods with no problems whatsoever.

The culprit? Colonies of cyanobacteria called Nostoc commune.

Cyanobacteria are single-celled organisms that can exist in multicellular states with chains of cells stuck together within a thin sheath to form a filament. This allows the cells to communicate and share nutrients over a large area which is how many Nostoc species form large mats.

The very odd appearance of hydrated Nostoc commune (Figure 1) is responsible for several common names. It was once believed the alien masses originated from the dust of shooting stars (aka meteors) which accounts for the common names of star-jelly, star-shot, and star-slime. Other common names such as 'witches' butter' are self-explanatory.

Drying (Figure 2) occurs quickly and does no harm to the cyanobacteria. It's actually a survival strategy supported by a range of polymers that keep the overall structure intact.

The good news: Nostoc commune is not toxic to plants or animals. However, when wet they can become quite slippery so be careful walking on it.


Water. Nostoc spp. are terrestrial organisms that can survive long periods of dehydration. However, they must have periodical infusions of water to thrive. Moisture management through improved drainage is essential.

Fertilizer. Although Nostoc can generate its own food and grab nitrogen from the atmosphere, it must acquire other nutrients from its environment. Phosphorus is considered the most nutrient-limiting in Nostoc development.

Chemicals. Algaecides such as carbonate peroxyhydrate and copper sulfate products provide limited to no control of Nostoc. Herbicides like glyphosate (e.g. Roundup) not only provide no control but the release of phosphorus from dead plants can actually support Nostoc growth.

Scythe (pelargonic acid) not only killed the Nostoc but also prevented regrowth for several weeks. It is labeled for the treatment of algae, moss, or liverworts, and other green vegetation and is considered a non-selective herbicide. Hydrated Nostoc must be targeted as dried mats are not susceptible. Always use pesticides according to their label.

Information for this article comes from the Buckeye Yard & Garden onLine from The Ohio State University. More specifically, Dr Joe Boggs is the author (reprinted with his permission). For more information, contact the Pulaski County Extension Service at 606-679-6361.

The Lake Cumberland Master Gardeners have pine straw mulch for sale at the Pulaski County Extension office. It is sold in bales for $7 per bale (over 50, $6 per bale). It can be purchased during office hours 8am to 4:30pm Monday - Friday.

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Come learn all about growing culinary herbs on May 16 at 6pm. It will be held at the Pulaski Co Extension office. Call us at 606-679-6361 and let us know you're coming.

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