Sunday, September 27, 2009


Don’t worry, there’s nothing unappealing here. This is just sort of another type of plant. You are looking at a collection of cyanobacteria known as Nostoc. Cyanobacteria are a type of photosynthetic bacteria. This means that they capture energy from sunlight in the same manner as green plants.

Nostoc generally grows in areas of poor barren soil and is not really noticeable until heavy rains wash a bunch of it into a pile. This shot was taken along the edge of my gravel driveway. The same phenomenon occurs in the barrens, but the effect is not as dramatic as here.

A Nostoc colony is composed of long strands of bacteria contained within a gelatinous membrane. After being moved along by water, the colony looks like a green blob.

The blob can be rolled out to show that the colony is actually a thin layer. As the colony grows, this thin layer moves out across the soil surface. It requires moisture in order to function and grow. During times of dry weather the colonies dehydrate and resemble dark green or black cornflakes. Heavy rains hydrate the colonies and move them around.

Nostoc has the ability to convert atmospheric nitrogen into organic forms usable by plants. This makes the Nostoc a valuable aid to plants trying to colonize bare, low fertility soils. It’s also funny to hide a Nostoc colony in the palm of your hand and watch people’s reactions when they think you’ve sneezed out something really nasty.


  1. ...very interesting. You might be able to solve a mystery that goes back to this July. I was in Hocking Hills when I saw a gelatinous, wormy and segmented thing growing on a tree. I saw it after the fact...I was taking a photo of a bird and it showed up in the background. Out of 30 comments, no one knew what it was. It reminds me a touch of your Nostoc... It's from July 13, 2009. I don't know if this link will work through comments, but here it is:
    If anyone can solve this can! It's at the bottom of the post.

  2. How interesting. I've seen this around, especially in its dried state, and always half-assumed it was some kind of algae or terrestrial lichen -- not that I'd ever heard that such things existed. I'll be much more respectful of it from now on.

  3. It actually forms a microscopically thin film of its cells on the surface of the substrate it's growing on. When rainwater dissolves nutrients in the soils or rocks it grows on, it usually has no competitors and grows to form the large green colonies you have pictured. When they dry out, they form cysts that grow into biofilms or colonies.

  4. Thanks for the information, Lorenzo.

  5. I've read site after site on this subject, but still have read no sure-fire methods to rid this stuff. How can this be done????

  6. Sorry, Ed. I'm afraid I don't have an answer for you. I've never given any thought to how to eliminate nostoc.