A few years ago, in July, I was at a reception where this young man was getting ready to head into basic training. One of my friends from church came up to me at this point and asked me about this green stuff — almost like green Jello — on their driveway.
She said, “We have had this stuff for several years. This green mass almost looked like it
would not occur naturally on Earth.”
As always, I prefer checking the problems out first-hand. What I saw was these green globs on their drive.
Then it struck me that there may have been some meteorite activity the week that this green glob showed up. Steve McQueen starred in a movie called the Blob in 1957 and it was the summer.
I did not have a stick to poke it like Larry did in the movie. It did seem like it was growing when I saw it. The gravel drive was in the sun, and it had just finished raining.
According to my friends, this material usually appears after it stops raining. This couple referred to this material as algae. From what they said, it disappears after the sun has been out for a short time, turns black in the sun, and appears to be growing.
The good thing is that it retreats into the gravel, leaving a paper-thin black patch on the ground.
From what I can see, we are looking at a type of cyanobacteria called Nostoc algae. Nostoc is also called “star jelly” or “spit of the moon.”
As I have progressed in my research on this material, I have seen that the blue-green algae are oxygen producers.
What we are looking at are colonies composed of filaments of moniliform cells, enclosed in a gelatinous sheath of polysaccharides. Some good news is that this material doesn’t harm anything, including grass or other plants or even Larry.
But it does indicate that the conditions aren’t good for plant growth. The ground where we found this material was clay under the gravel and compacted.
We were not in the shade, and it did not stay moist most of the time. If you do have some of this stuff in your yard, you can see all or part of these conditions: clay or silt soil that is probably compacted, poorly drained, and shade.
If you want to know which conditions would harm your grass, all you need to do is look at the conditions I just described.
To really understand and identify Nostoc, we need a microscope to get a close look.
This plant, as I said, is an unbranched filamentous organism, and many filaments are aggregated or clumped together within a gelatinous mass to form a colony. Each colony is greenish to bluish-green in color and contains many contorted or twisted trichomes.
These strands or trichomes are composed of rounded or oval cells. What is odd is that these cells arrange themselves in a single row, like beads on a string. You may see different colors in the cells due to other pigments, such as chlorophyll, phycocyanin, or phycoerythrin.
Each of these strands contains specialized cells called heterocysts that fix atmospheric nitrogen used during nitrogen starvation. They create a microanaerobic environment to protect the nitrogen-fixing enzyme nitrogenase from oxygen.
This enzyme action allows the cyanobacteria to provide nitrogen from biosynthesis while relying on neighboring cells for carbohydrates.
When nostoc algae are stressed, they enter a vegetative form of reproduction called hormogonia. The fertile filaments of unicellular, filamentous cyanobacteria reproduce, and some may contain heterocysts and akinetes. In response to a hormogonium-inducing factor (HIF) secreted by plant hosts, cyanobacterial symbionts differentiate into hormogonia.
This hormogonium differentiation is crucial for the development of this nitrogen-fixing plant, as it differentiates back into vegetative cells after 96 hours. For this to have occurred, these filaments would have needed to find a plant host.
Changing the conditions in which this green glob grows will help stop the plant.
Therefore, aerate the soil, eliminate the wetness around the area, and remove the shade. I have discovered that sprinkling baking soda over the nostoc algae will kill it.
Various algaecides should kill this material, but copper applied to anything will cause a number of environmental problems. Copper has a profound effect on both birds and fish and is a heavy metal.
One little clue about this stuff is that when it turns black, it is only dormant and will come back, but when you apply baking soda, it turns brown.
What we learned is that we should not just poke green globs with a stick but use baking soda.
If you have questions after your stroll this week, e-mail me at ericlarson546@yahoo.com. I will answer the question.
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